Hot start problem resolved due to failed check valve in the DMCH fuel pump

[cybercusp]

I finally got rid of the hot start problem due to the failed check valve in the new DMCH fuel pump combo. I installed the S.U.R. and R. check valve. http://img.tapatalk.com/d/13/09/03/a9anudy6.jpg

It took about thirty minutes and after 3 days of running it I've not had a single hot start issue. Hopefully this is now a non-issue; my thought is an external check-valve will be an included item in the revised DMCH fuel pump combo.

A few shots of the installation...fairly straight forward.
http://img.tapatalk.com/d/13/09/03/ajuquru3.jpghttp://img.tapatalk.com/d/13/09/03/ejuvuhe7.jpghttp://img.tapatalk.com/d/13/09/03/a2eqyryr.jpghttp://img.tapatalk.com/d/13/09/03/unune4us.jpg

[Ryan S.]

I installed mine over a month ago and still works. Mine is located much closer to the pump. The kit didn't come with hose clamps but fortunatly I had some left overs from accumulator job.
i think amazon was a little cheaper.

[David T]

I finally got rid of the hot start problem due to the failed check valve in the new DMCH fuel pump combo. I installed the S.U.R. and R. check valve. http://img.tapatalk.com/d/13/09/03/a9anudy6.jpg

It took about thirty minutes and after 3 days of running it I've not had a single hot start issue. Hopefully this is now a non-issue; my thought is an external check-valve will be an included item in the revised DMCH fuel pump combo.

A few shots of the installation...fairly straight forward.
http://img.tapatalk.com/d/13/09/03/ajuquru3.jpghttp://img.tapatalk.com/d/13/09/03/ejuvuhe7.jpghttp://img.tapatalk.com/d/13/09/03/a2eqyryr.jpghttp://img.tapatalk.com/d/13/09/03/unune4us.jpg

In fact, it is probably a good way to fix a problem with the check valve in the OEM pump setup too. The only question remaining is how it will hold up to E-10 fuel. Just be SURE to install it in the correct direction!!!!!!
David Teitelbaum

[Patrick C]

I was unaware that the new DMCH unit was having such problems with check valves. Good fix you developed here!

[refugeefromcalif]

I just ordered my check valve. :)

George

[Josh]

I am going to be ordering one of these pump/sender combos in the near future, I find it very dissapointing that this is the fix if it is a common problem. I will be spending 400+shipping+duties, and I do not want to be spending 40+shipping more.

[NightFlyer]

I am going to be ordering one of these pump/sender combos in the near future, I find it very dissapointing that this is the fix if it is a common problem. I will be spending 400+shipping+duties, and I do not want to be spending 40+shipping more.

Yep it is a very known problem - even on units that should be good according to DMCH's supplier (such as mine). But you don't need to buy such an expensive check valve. Unless you want to be adding an external in-line check valve later, then I suggest doing it when you install the pump/sender combo, if not for anything more than insurance.

Here's the one that I just ordered - $14 including worldwide shipping, ships from Memphis, TN:

http://i.ebayimg.com/t/5-16-Check-Valve-Diesel-or-Gas-8mm-One-Way-Fuel-Flow-/00/s/NjQwWDYxNg==/$(KGrHqJ,!jQE9Nl0y-tIBPlHwcGRlg~~60_12.JPG

http://www.ebay.com/itm/5-16-Check-Valve-Diesel-or-Gas-8mm-One-Way-Fuel-Flow-/281150456580?pt=Motors_Car_Truck_Parts_Accessories&hash=item4175df8304&vxp=mtr

Or, you can get the $8 plastic unit, including worldwide shipping, ships from Miami, FL:

http://i.ebayimg.com/t/5-16-8mm-One-Way-Valve-Check-Valve-/00/s/Mzc0WDQwMA==/z/tugAAMXQ7j1SISxl/$T2eC16Z,!zgFIdUEhm+wBSIS)luGhg~~60_12.JPG

http://www.ebay.com/itm/5-16-8mm-One-Way-Valve-Check-Valve-/161097227896?pt=LH_DefaultDomain_0&hash=item2582249e78&vxp=mtr

[Bitsyncmaster]

I don't see a pressure rating on that plastic valve. Looks like a vacuum type check valve. I would never trust it for 75 PSI fuel.

[DMC5180]

I am going to be ordering one of these pump/sender combos in the near future, I find it very dissapointing that this is the fix if it is a common problem. I will be spending 400+shipping+duties, and I do not want to be spending 40+shipping more.

You may Not have any issue with your combo/sender unit. But nothing is 100% failure proof. I don't see a need for you to get the Extra Check valve (insurance) unless you choose too. Even then you should be able to find a suitable check valve in CANADA.

[Josh]

You may Not have any issue with your combo/sender unit. But nothing is 100% failure proof. I don't see a need for you to get the Extra Check valve (insurance) unless you choose too. Even then you should be able to find a suitable check valve in CANADA.

Yeah I know I can find the CV. However what I was getting at is buying a drop in solution for the pump/sender and having to upgrade parts right off the hop.

[NightFlyer]

I don't see a pressure rating on that plastic valve. Looks like a vacuum type check valve. I would never trust it for 75 PSI fuel.

I'm with you Dave, however, other owners have reported using a similar black plastic unit from China with supposedly great success:

http://i.ebayimg.com/t/5-16-8mm-Inline-Check-Valve-Fuel-Diesel-Gas-Pump-Liquid-One-Way-Non-Return-/00/s/MjAwWDMwMA==/$(KGrHqZ,!q4FCS9S(H2KBQt)U4(JvQ~~60_35.JPG

http://www.ebay.com/itm/5-16-8mm-Inline-Check-Valve-Fuel-Diesel-Gas-Pump-Liquid-One-Way-Non-Return-/221274031402?pt=Motors_Car_Truck_Parts_Accessories&hash=item3384f5c52a&vxp=mtr

Personally, I wouldn't trust either of these plastic units as far as I could throw them - I just wanted Josh to know that there were many alternative check valves available (although I'm quite certain that he already knew that).

Again, according to DMCH's supplier, my unit shouldn't have a check valve issue. Purchased a little over a month ago via DMC-Midwest. However, I've had quite a few hot start issues since installation. Everything else in the fuel system has either been replaced with new (accumulator, filter, soft lines, one hard line, distributor) or double checked, thus I'm quite certain it's the fuel pump check valve in my new combo unit. We'll find out soon enough I guess...

[Jimmyvonviggle]

Can someone explain to me what this thing does. I'm a little disappointed if there is a problem with the new unit they don't send out a letter or a fix for it.

[ssr60]

I’ve been having starting problems ever sense I installed the new DMCH fuel pump unit. Emailed and talked with DMCH James and Steve on several occasions. They didn’t think the problem was related to the new pump. I replace the fuel accumulator still had the problem. Had the fuel pressure tested last week and lost all pressure within 10 minutes. Worse $400 I ever spent. I should go back to the Tuna can.............

[Rich]

Can someone explain to me what this thing does....
All of the Bosch OE and Bosch replacement fuel pumps for the K-Jet have an internal check valve. The check valve prevents fuel from returning to the tank after the pump turns off. It has to seal well, along with all of the other bits in the primary fuel loop, in order to maintain fuel rest pressure.

If a replacement pump has a faulty check valve then the fuel rest pressure will be lost too quickly resulting in difficulty with hot starts.

Some folks are resorting to a workaround for what seems to be a problem with the internal check valve in at least some of the replacement pumps.

[virtualchuck]

All of the Bosch OE and Bosch replacement fuel pumps for the K-Jet have an internal check valve. The check valve prevents fuel from returning to the tank after the pump turns off. It has to seal well, along with all of the other bits in the primary fuel loop, in order to maintain fuel rest pressure.

If a replacement pump has a faulty check valve then the fuel rest pressure will be lost too quickly resulting in difficulty with hot starts.

Some folks are resorting to a workaround for what seems to be a problem with the internal check valve in at least some of the replacement pumps.So is the consensus here that an external check valve should be installed as a preventative measure when installing a new pump?

Chuck

[Bitsyncmaster]

So is the consensus here that an external check valve should be installed as a preventative measure when installing a new pump?

Chuck

Pretty easy to do a rest pressure test before and after you install the pump. So get the hours it holds rest pressure. Installing a check valve after is also easy to do.

[Delorean02378]

I've got a brand new DMC fuel pump sitting in a box waiting for the current pump and sender to go bad. I hate that people are experiencing problems with these. In my business, a RECALL would have been issued a long time ago. Remember the Firestone tire incident? It wasn't the tire manufacturer that issued the recall, it was vehicle manufacturer that issued the recall.

Worst case scenario, the pump fails while on the road and causes an accident, since it's a documented known issue, guess who finds themselves in a legal mess.

[NightFlyer]

I've got a brand new DMC fuel pump sitting in a box waiting for the current pump and sender to go bad. I hate that people are experiencing problems with these. In my business, a RECALL would have been issued a long time ago. Remember the Firestone tire incident? It wasn't the tire manufacturer that issued the recall, it was vehicle manufacturer that issued the recall.

Worst case scenario, the pump fails while on the road and causes an accident, since it's a documented known issue, guess who finds themselves in a legal mess.

The known issue with the check valves really only effects rest pressure, and causes hot start issues. I don't see how it would cause a failure while the pump is operational and lead to an accident. While it could leave you stranded until the engine cools (assuming you don't know how to trick the cold start valve into firing), that would be about the worst of it.

[Henrik]

The CV should be installed on the supply side of the loop I assume?

[NightFlyer]

The CV should be installed on the supply side of the loop I assume?

Yes - on the output from the fuel pump to the accumulator.

[cybercusp]

Yes - on the output from the fuel pump to the accumulator.

+1
It should be installed/spliced within the hose that leads to the innermost hard fuel line..the hard line closest to the middle of the car; that should be the sending line from the fuel pump to the engine and the one that will be getting the check valve.

I'm at a week now of driving it daily and still no hot start problems. It fires immediately no matter how long it's been sitting.

[rothsean]

+1
It should be installed/spliced within the hose that leads to the innermost hard fuel line..the hard line closest to the middle of the car; that should be the sending line from the fuel pump to the engine and the one that will be getting the check valve.

I'm at a week now of driving it daily and still no hot start problems. It fires immediately no matter how long it's been sitting.

Me too, I am at 3 weeks and it fires quickly. I installed the $7 black plastic CV.

[refugeefromcalif]

I also added an In-Line Check Valve yesterday.
I have the New DMCH fuel pump combo, and for $399.99 It's cost me more in headaches, (And diagnostic $$$), then my old fuel pump and Inaccurate sender.
It's only been 48 hrs. but, my car starts Any time so far. Hot or Cold. I haven't had access to a fuel pressure gauge though and check Rest Pressure.

Here's a couple pics of my install on the fuel FEED line.

http://dmctalk.org/attachment.php?attachmentid=21807&d=1378665167

http://dmctalk.org/attachment.php?attachmentid=21808&d=1378665356

George

[refugeefromcalif]

Question for those with the New fuel pump combo and have added a Check Valve.

How many are Wanting/trying to return their units for replacement? (Hoping for an integrated check valve in the combo that works)..

I'm on the fence on this. Do I mess with something that now Works or, go back to possibile starting problems?

George

[Jimmyvonviggle]

Question for those with the New fuel pump combo and have added a Check Valve.

How many are Wanting/trying to return their units for replacement? (Hoping for an integrated check valve in the combo that works)..

I'm on the fence on this. Do I mess with something that now Works or, go back to possibile starting problems?

George

I think it's easier to just buy the extra check valve than removing it,shipping it back, and waiting for a new one. Of course there are those that will do this to maybe prove a point, and I understand this feeling.

[NightFlyer]

Question for those with the New fuel pump combo and have added a Check Valve.

How many are Wanting/trying to return their units for replacement? (Hoping for an integrated check valve in the combo that works)..

I'm on the fence on this. Do I mess with something that now Works or, go back to possibile starting problems?

George

Not worth it IMHO. I'm all about functionality. The unit works great (or at least appears to thus far) other than the inherently bad internal check valve problem. BTW, the external in-line check valve that I ordered just arrived in the mail today - will be installing it sometime during the next couple days. I just had another hot start problem today, despite DMCH insisting that my unit should have a good/working internal check valve. The worst part about a hot start problem is that they always seem to happen when you have people gawking at the car - it's embarrassing. We'll find out if in fact my problem is the internal check valve on the fuel pump/sender combo unit soon - although I strongly suspect it is, as everything else still checks out 100% after a triple check of the entire fuel system.

The only way that I'd even consider returning the unit under a warranty claim for a replacement is if they were offering the unit without an internal check valve all together, as then I could just rely solely on the external in-line check valve. In fact, I haven't even complained about my current situation to either Midwest (where I purchased the unit) or Houston - it is what it is and the fix is reasonably affordable and easily doable. Like I said before, I'm thankful that Houston is even out there and offering re-designed/re-engineered products such as this, so while I don't expect perfection (as many here seem to do), as long as the product they're selling is at least 90%, I'm cool with it and will be thankful for the support that they provide to the community. After all, what other marque with about 6,500 remaining vehicles, and about 2,000 or less that are actually roadworthy, have the kind of product support and development that we as DeLorean owners enjoy with our vendors? Personally, I can't think of any.

[StainlessBullet]

I've got a brand new DMC fuel pump sitting in a box waiting for the current pump and sender to go bad.

Same here. I was one of the first that bought this combo kit when it came out. Mine is still in the box and never been used too. I was planning to install it on my project car when it got to that point, but now I'm not so sure.

I agree it would be nice if DMCH sent out letters to their customers letting them know about these problems, especially after spending $400+ on something. I didn't know anything about this issue until Josh @ DPI posted about it on facebook.

[thirdmanj]

Same here. I was one of the first that bought this combo kit when it came out. Mine is still in the box and never been used too. I was planning to install it on my project car when it got to that point, but now I'm not so sure.

I agree it would be nice if DMCH sent out letters to their customers letting them know about these problems, especially after spending $400+ on something. I didn't know anything about this issue until Josh @ DPI posted about it on facebook.

Sounds like the problem is easily corrected with a check valve. Perhaps DMCH should send out a complimentary check valve to everyone who purchased one?

[StainlessBullet]

Sounds like the problem is easily corrected with a check valve. Perhaps DMCH should send out a complimentary check valve to everyone who purchased one?

That would work too. I still think at least a letter should be sent out to everyone that could be affected. The people that are not on this forum will have some troubleshooting to do if they start having problems.

[refugeefromcalif]

The worst part about a hot start problem is that they always seem to happen when you have people gawking at the car - it's embarrassing.

+1.
Although my car gave me problems everywhere, it Really bothered me when a crowd was around...


The only way that I'd even consider returning the unit under a warranty claim for a replacement is if they were offering the unit without an internal check valve all.

After all, what other marque with about 6,500 remaining vehicles, and about 2,000 or less that are actually roadworthy, have the kind of product support and development that we as DeLorean owners enjoy with our vendors? Personally, I can't think of any.

It still Amazes me that we have a nice group of venders available for a car that, (Let's face it), wasn't a Big success when it was new. (Compaired to other cars).

I've decided to keep what's working until it doesn't. :)

George

[Silverbullet]

Ok.... had the combo unit for over a year now (got in July 2012) and never had a problem... but for $9.98 delivered, I installed the check valve... Hope it is never a problem now...
http://i116.photobucket.com/albums/o19/AtHomeSoda/ComboPumpCheckValve_zps49c25eae.jpg (http://s116.photobucket.com/user/AtHomeSoda/media/ComboPumpCheckValve_zps49c25eae.jpg.html)

[jawn101]

What's the consensus on the eBay plastic valve? Durable enough to rely on, or is the metal one really worth 4x as much?

[Ron]

I'm with Bitsy on that. If it is rated for 100+ psi and fuel, it's probably ok.. But if I couldn't see it in black and white, I'd look elsewhere.

[Tillsy]

What's the consensus on the eBay plastic valve? Durable enough to rely on, or is the metal one really worth 4x as much?

There's are cheaper metal ones available, scrub the example I gave though not rated for high pressure.

[NightFlyer]

Due to a couple of questions I've received from members, I wanted to update this thread in regards to the check valve that I purchased. The valve I initially purchased is in an aluminum housing and looks like this:

http://i.ebayimg.com/t/5-16-Check-Valve-Diesel-or-Gas-8mm-One-Way-Fuel-Flow-/00/s/NjQwWDYxNg==/$(KGrHqJ,!jQE9Nl0y-tIBPlHwcGRlg~~60_12.JPG

I purchased it from here for $14 shipped: http://www.ebay.com/itm/5-16-Check-Valve-Diesel-or-Gas-8mm-One-Way-Fuel-Flow-/281150456580?pt=Motors_Car_Truck_Parts_Accessories&hash=item4175df8304&vxp=mtr

They have since hiked the price significantly - currently $22.95 shipped.

I haven't installed it yet though, and probably won't, as I can't find any hard specs for this thing anywhere. And while it seems like it should work and probably will, I've found on other sites with valves of a similar appearance that they're only rated to hold up to 25 psi of back pressure. So, while I'm sure it would work initially, I'm guessing that it would probably wear out in a relatively short amount of time given the pressure our system works with.

So, just today, I ordered one of these:

http://www.usplastic.com/catalog/images/products/Valves/sku/22398psku.jpg

I purchased it here for $11.08 plus shipping: http://www.usplastic.com/catalog/item.aspx?itemid=85394&catid=945

It's a piston valve in a brass housing with an inner viton seal. Cracking pressure is 1psi and it's rated to hold a back pressure of up to 500psi, so you know it'll work all the time and should never wear out given the pressure our fuel systems run at. Not to mention that due to the recent price hike on the initial valve that I ordered, the US Plastics valve is significantly cheaper.

Thus, I'm changing my recommendation to the brass US Plastics valve, for all those interested.

[Josh]

Can we get someone to chime in on this thread from DMC? I still find this band aid fix ridiculous. I love the idea of the integrated sender / pump but I am not going to purchase it if this is the fix. I think it is silly enough that the fuel lines are clamped together...

[NightFlyer]

Can we get someone to chime in on this thread from DMC? I still find this band aid fix ridiculous. I love the idea of the integrated sender / pump but I am not going to purchase it if this is the fix. I think it is silly enough that the fuel lines are clamped together...

Here's a response from James Espey of DMCH regarding the situation with the pump/sender combo units faulty check valves:


First, it's *six* month warranty - not three - it's printed on the line item for every invoice (along with the disclaimer about fuel tank contamination voiding the warranty). If someone told you three, they were mistaken.

Next, since you haven't contacted us about the second failure I encourage you to do so - with this product we have been very liberal with replacements for failed check valves, and here's why:

We tested three units on three different cars for nearly a year in three separate parts of the country. As you recall, we first showed this unit at our open house in the summer of 2011 - and production units didn't really start to ship until May/June of 2012. We had zero problems with any of the test units. We've had about an 8% failure rate on the first batch of about 250 or so units, and SOME of the those were swapped out with later units FROM THAT SAME BATCH which in a few more cases exhibited the same check valve failure.
Based on this, we went back to our supplier and as of February of this year they have been supplying units with a different pump. These pumps have performed well and the only failures (3 to date) on those were ALL due to fuel tank contamination upon inspection of the failed pumps/filters. Units with the later pumps can be identified by the letter "A" at the end of the serial number affixed to the controller box. As of June, we are also hot stamping the letter "T" on the fuel modules with the later pump or that have had the pumps replaced under warranty.

Now that we've been about six months on these new units, with the aforementioned good results, we've determined that we will extend the warranty on each unit that was originally sold prior to February 2013 by an additional 12 months. This is done on an exchange basis, simply contact your selling dealer to have this exchanged. As always, units that exhibit fuel tank contamination are not covered under warranty, but *may* be able to be repaired by the dealer for a nominal parts & labor charge. Letters to the this effect are going out early next week, once we are sure that we have identified all the purchasers of this part. The majority of them were sold by our dealers (not DMCH) so we're working with them to get this list as correct as possible.

We're also working with our supplier to develop a "user -installable" replacement pump, and have actually sent a couple of these out to a few users to test - this will mean that the user can replace the pump down (or on the side) of the road should they experience a failure in the future.

It can be found here: http://dmctalk.org/showthread.php?7983-What-incentive-does-DMC-or-its-franchises-have-for-making-super-reliable-parts&p=117736&viewfull=1#post117736

While their supplier claims that the issue has been resolved in newer units, the unit that I purchased and installed 2 months ago, with "the letter 'A' at the end of the serial number affixed to the controller box," has started to exhibit the signs of a failing/failed internal check valve.

Hope this helps!

[Josh]

Here's a response from James Espey of DMCH regarding the situation with the pump/sender combo units faulty check valves:



It can be found here: http://dmctalk.org/showthread.php?7983-What-incentive-does-DMC-or-its-franchises-have-for-making-super-reliable-parts&p=117736&viewfull=1#post117736

While their supplier claims that the issue has been resolved in newer units, the unit that I purchased and installed 2 months ago, with "the letter 'A' at the end of the serial number affixed to the controller box," has started to exhibit the signs of a failing/failed internal check valve.

Hope this helps!

Thank you for the information Josh! I will keep this in mind.

[DeLorean03]

Hey Nightflyer, I just ordered the check valve you suggested for about $20 (with shipping included). I have had "interesting" starting issues for weeks now - basically if it sits for about a day = 3-5 seconds before it starts, but if it sits for 3-4 days = nearly perfect start everytime.


We're going to find out once and for all if it's the check valve on my unit. Soon.......

[Silverbullet]

Ok.... had the combo unit for over a year now (got in July 2012) and never had a problem... but for $9.98 delivered, I installed the check valve... Hope it is never a problem now...
http://i116.photobucket.com/albums/o19/AtHomeSoda/ComboPumpCheckValve_zps49c25eae.jpg (http://s116.photobucket.com/user/AtHomeSoda/media/ComboPumpCheckValve_zps49c25eae.jpg.html)

Ok,... The plastic Check Valve, is rated for high pressure, intended use is for diesel use... it is $9.98 delivered... Did ANYONE notice the top of the NEW fuel pump... it is PLASTIC... Oh my God... it will fail... REALLY????

Craig

[NightFlyer]

Hey Nightflyer, I just ordered the check valve you suggested for about $20 (with shipping included). I have had "interesting" starting issues for weeks now - basically if it sits for about a day = 3-5 seconds before it starts, but if it sits for 3-4 days = nearly perfect start everytime.


We're going to find out once and for all if it's the check valve on my unit. Soon.......

I hope you got the SMC 410 series brass piston valve with an inner viton seal from US Plastics Corp. They're located in Lima, OH, so not too far from you. My order plus USPS priority mail shipping came to a total of $17.46. It should look like this:

http://www.usplastic.com/catalog/images/products/Valves/sku/22398psku.jpg

Oops - never mind. I just figured out why it may have cost you a little more than it cost me even though I'm further away from their location. As you're shipping to an OH address and the company is located in OH, you had to pay OH sales tax, whereas I didn't have to pay any sales tax.

This is the best valve for our application that I could find. While the more expensive S.U.R. & R. brass/steel valve (about $40) looks solid and works just fine (as many here are already using it), I can't find specs on it anywhere, including on the manufacturer's website, which just offers a general description. Add to that, it's merely a pre-assembled NPT threaded valve, which means there are two additional joints that could potentially leak if bad or ever failed. The same can be said for any other in-line NPT threaded valve that would require the addition of 5/16" brass hose barbs to install in our application.

I like the SMC 410 series valve as the casing is solid brass with no additional joints to potentially leak and cause problems.

And while ordering a product made in China from a US seller/importer/retailer is bad enough as it is, I adamantly refuse to order anything made in China directly from a Chinese seller, which is why I wouldn't even consider the black plastic unit that others have purchased from eBay and are using. While I'm sure they'll work just fine for a while, there's not much headroom on the specs of those valves, thus I don't see them as lasting as long as the SMC valve.

Again, everyone should disregard the initial valve that I purchased from eBay and was recommending, as it's for low pressure applications and not suitable for our application. You want the one pictured in this post from US Plastics Corp - the SMC 410 series solid brass valve. Here's the link once more for those interested:

http://www.usplastic.com/catalog/item.aspx?itemid=85394

I'll be sure to update my results once the valve in received and installed. Hope it fixes DeLorean03's problems as well, even though his K-Jet based woes will soon be forever nullified :thumbup2:

[NightFlyer]

Ok,... The plastic Check Valve, is rated for high pressure, intended use is for diesel use... it is $9.98 delivered... Did ANYONE notice the top of the NEW fuel pump... it is PLASTIC... Oh my God... it will fail... REALLY????

Craig

Who's saying it will fail because it's plastic? As I previously stated, I'm sure it'll work just fine, for a while anyway.

Personally, I don't like it because 1) it's made in China; and 2) you need to purchase it directly from a Chinese seller in order to get it for the best price possible.

BTW, here's the specs on that valve for those interested: Claims to have an inner viton seal, cracking pressure is .3psi, and it's rated to hold a back pressure of up to 116psi.

So, while there's some headroom with this valve, it's not much. More headroom = longer life expectancy before failure.

[NightFlyer]

As there seems to be a lot of interest in this, I decided to post this here.

There are many options of in-line check valves available, ranging from a simple plastic valve all the way up to brass/steel valves.

At the top of the price range, you'll find the S.U.R. & R. brass/steel kit. I'm unable to find the specs on this valve anywhere, including at the manufacturer's website, which only gives a general description of the valve. Note that it appears to be little more than a standard NPT threaded valve pre-assembled with multi-union connectors. While there's nothing wrong with this, it does add two additional joints into the fuel system that could potentially leak/cause problems if they're bad or ever fail. It looks like this:

http://i.ebayimg.com/t/Fuel-Line-Check-Valve-for-3-8-Lines-SRRCKV7-BRAND-NEW-/00/s/MjUwWDI1MA==/$(KGrHqN,!g0E5o,VQpVnBOiKzwGZfQ~~60_35.JPG

It can be purchased for $38.05 shipped from here: http://www.ebay.com/itm/SUR-R-CKV5-5-16-Check-Valve-1-/290966078207#vi-content

In the middle of the price range, you'll find the SMC 410 series solid brass piston valve with an inner viton seal. Cracking pressure is 1psi and it's rated to hold a back pressure of up to 500psi - plenty of headroom to ensure perfect performance and ultra longevity. It looks like this:

http://www.usplastic.com/catalog/images/products/Valves/sku/22398psku.jpg

It can be purchased for $11.08 plus shipping from here: http://www.usplastic.com/catalog/item.aspx?itemid=85394&catid=945

At the bottom of the price range, you'll find a generic Chinese made opaque plastic valve with an inner viton seal. Cracking pressure is 2.2psi and it's rated to hold a back pressure of up to 145psi. It looks like this:

http://i.ebayimg.com/t/5-16-8mm-One-Way-Valve-Check-Valve-High-Pressure-/00/s/MzgyWDQwMA==/z/tSwAAOxyVPJSIS9H/$(KGrHqR,!nwFIJHTVuJtBSIS9HKUh!~~60_12.JPG

It can be purchased for $7.99 shipped from here: http://www.ebay.com/itm/5-16-8mm-One-Way-Valve-Check-Valve-High-Pressure-/151112059985?pt=LH_DefaultDomain_0&hash=item232efb0c51&vxp=mtr

Another popular budget choice in the community is a generic Chinese made black plastic valve with an inner viton seal. Cracking pressure is .3psi and it's rated to hold a back pressure of up to 116psi. It looks like this:

http://i.ebayimg.com/t/5-16-8mm-Inline-Check-Valve-Fuel-Diesel-Gas-Pump-Liquid-One-Way-Non-Return-/00/s/MjAwWDMwMA==/$(KGrHqZ,!q4FCS9S(H2KBQt)U4(JvQ~~60_35.JPG

It can be purchased for $9.98 shipped from here: http://www.ebay.com/itm/5-16-8mm-Inline-Check-Valve-Fuel-Diesel-Gas-Pump-Liquid-One-Way-Non-Return-/321189616994?pt=Pneumatic_Hydraulic_Valves_Parts&hash=item4ac8649d62

While there are other compatible in-line check valves available, you really need to confirm the back pressure they're rated to hold back, as many valves are rated for low pressures only - around 25psi. The aluminum valve I initially purchased for myself and was recommending turned out to be of a low back pressure rating and insufficient for the needs of our fuel system. For our fuel systems, you want a valve rated at a minimum of 100psi. With greater headroom in the back pressure rating, you can expect better performance and greater longevity of the valve.

Thus, I personally opted for and recommend the middle price range SMC 410 series solid brass piston valve with inner viton seal from US Plastic Corp.

I hope this helps those using DMCH's new fuel pump/sender combo unit!

[NightFlyer]

It's confirmed - the SMC 410 solid brass casing valve features internal grade 302 stainless steel construction with a viton seal and is proudly MADE IN THE USA!!!

http://www.usplastic.com/catalog/images/products/Valves/sku/22398psku.jpg

http://valves.specialtymfg.com/product/check-valves-brass-stainless-steel/410-series-piston-check-valve?

Again, it can be purchased for $11.08 plus shipping from here: http://www.usplastic.com/catalog/item.aspx?itemid=85394&catid=945

Anyone who even considers going with another valve is out of their gourd IMHO!!!

[DeLorean03]

I'll be sure to update my results once the valve in received and installed. Hope it fixes DeLorean03's problems as well, even though his K-Jet based woes will soon be forever nullified :thumbup2:

Well, while this is true, we tentatively do plan to keep the DMCH combo pump. With that being said, my injectors will be spraying fully at 42-44 psi, so yeah - won't be anywhere near the stress of the KJet system. Still, I didn't want to leave anything left to chance. I noticed this problem only started with the introduction of the combo unit, and while it was changed at DMCMW's open house, unfortunately, the problem has been rather persistant.

So, figured why not and try a quick $20 fix. If that doesn't fix it, then I know it's something else in KJet, which as you said, will be nullified soon enough :). I can go 1.5 more months like this ;).

Good work with all your recent posts, Nightflyer. You summarized it all very well, and you've made it easy for everyone to reference all the options quickly. Well done!

[Bitsyncmaster]

Here is my thoughts on the pump problem. The pump is probably used in thousands of cars or trucks (don't know where it comes from) without problems. But I'm willing to bet all those run 50 PSI EFI pressures. EFI is less prone to rest pressure problems. Now you would not think running 75 PSI should show up a design issue. It may also be the running of 10% gas all year round (which is new). It may be our car commonly sits for long periods of time. One big difference with our car is the gas in the tank gets to 130 deg. F.

It seems the real test for our D is 50 cars need to be equipped with most any new design to find bugs in the design. Every owner runs his car differently and has modified things differently.

[Ron]

I have had "interesting" starting issues for weeks now - basically if it sits for about a day = 3-5 seconds before it starts, but if it sits for 3-4 days = nearly perfect start everytime.


We're going to find out once and for all if it's the check valve on my unit. Soon.......???
If it sits a day, or more, a starting problem will have nothing to do with the check valve...

[Bitsyncmaster]

???
If it sits a day, or more, a starting problem will have nothing to do with the check valve...

+1


Try this. Pull the connector off you CSV and see it that fixes your startup. That would indicate your mixture is a little too rich.

[DeLorean03]

Thank you, guys. Pulled CSV and so far so good. Man....that was a "duh" moment on my part. Oh well, if someone needs this CV in the local community, now I have one to help them !

[Bitsyncmaster]

Thank you, guys. Pulled CSV and so far so good. Man....that was a "duh" moment on my part. Oh well, if someone needs this CV in the local community, now I have one to help them !

I don't run the CSV either because I found the engine will start better in the summer that way. But I have a hot start relay so if I crank longer than one second, it then turns on the CSV. My engine will need the CSV if it sets a long time or in the winter on a cold start.

[NightFlyer]

Just how many D owners purchased the SMC 410 in-line check valve this last weekend from US Plastics???

Mine shipped, but their website now shows them as being out-of-stock and currently on order.

Looking forward to getting and installing mine - hopefully all of my hot start problems will be a thing of the past :)

[DeLorean03]

Well, I can tell you my fuel mixture is good because I leaned it out, and I got a miss started as I was cruising at 3-5 mph through a parking lot. Enriched it back up as much as I leaned it, and my car runs great with no missing. So now it goes to air/compression/ignition/fuel - with air and compression being good, and I replaced my entire ignition system (coil in 2005, everything else this year) with the exception of the electrical distributor.

So, as usual, it probably goes back to KJet. All of my components are new except the 32 year cold start valve and fuel distributor, and at $189 and $450 - *Archer reference* NOOOAAAAAAPPPE! 1 month to go until Eddie gives me EFI, so I'll just deal with it. Car always starts, just takes 3-5 seconds. Will still be adding the check valve, and if that fixes it, you can be sure I'll let everyone know :D!

I know, I know..... it shouldn't fix it, but the fact that my fuel system was nearly flawless for 6-7 years, and then about the time I added the combo unit - which unfortunately is starting to have a nasty reputation for being $400 to "buy someone else's problems" - I can't help but eyeball it. We'll see what happens once it comes in.

[Ron]

Looking forward to getting and installing mine - hopefully all of my hot start problems will be a thing of the past :)???
Didn't you test it?

[NightFlyer]

???
Didn't you test it?

Are you thinking of the initial valve that I ordered off eBay? If so, I never installed that one as I don't believe it's rated to hold more than a 25psi back pressure, which would be inadequate for our application. However, I can't find documentation on this anywhere and the seller was unable to provide me with any concrete specs. This is also the reason why I didn't opt for the expensive S.U.R. & R. valve that others here have used with great success - the absence of specs and the fact that it's simply a NPT valve housing pre-assembled with multi-union connectors, thus creating two additional points that could potentially leak if faulty or ever failed.

I only just ordered the SMC 410 series valve on Sat. Should arrive on Wednesday. All the specs have been confirmed by both the retailer/seller (US Plastics) and the manufacturer (Specialty Manufacturing Corp), thus I have no doubt that it will work brilliantly for our application.

The SMC 410 series valve features a solid brass single piece housing, thus no additional joints unlike the S.U.R. & R. valve. The internals feature a grade 302 stainless steel piston valve with a viton inner seal that rests on the seat. It has a cracking pressure of 1psi and is rated to hold back pressures of up to 500psi. Plenty of head room for our systems, thus ensuring excellent longevity and reliability. And the best part is that it's MADE IN THE USA - Twin Cities metro region in Minnesota to be precise. I couldn't find where the S.U.R. & R. valve is made - perhaps someone who purchased this valve can tell us?

Whether or not it solves my hot start problems in particular remains to be seen, but everything else in the fuel system from the tank to the FD has been tested 3 separate times now and it all checks out as being fine, thus the only thing left to cause trouble is the fuel pump's internal check valve.

[Ron]

No no, I meant test the fuel system for hold pressure. ...you say, "if it fixes..."???

[NightFlyer]

No no, I meant test the fuel system for hold pressure. ...you say, "if it fixes..."???

Manually, yes. With pressure gauges, no.

[DeLorean03]

I have put fuel pressure gauges on my car more in one year than in the other 8 years combined - all when I intro'd this combo unit onto my car. I could have just thrown the gauges on my car, and I should have. With the staggering number of check valve failures we are seeing, I felt that $20 to be 100% without a shadow of a doubt sure was a minimal investment.

Also, since Eddie wants to keep this pump for the conversion to EFI, I don't want him chasing a ghost with a possibly defective check valve. With this installed, I know my fuel pump and check valve are bulletproof. The rest of the fuel system will be leaving...

[Jimmyvonviggle]

Just so I am clear on this, I put the valve on the line that goes from the pump that has the "F" designation?

[NightFlyer]

Just so I am clear on this, I put the valve on the line that goes from the pump that has the "F" designation?

The output/feed/supply line that runs to the accumulator - not the return line.

[DeLorean03]

Installed mine today. Looks great! Put electrical tape on the clamps to keep the return hose safe from the sharp corners of the injection clamps.

22121

22122

Didn't fix my cold start issue - was on the fence about it. Fired up absolutely flawlessly after sitting a week. Gave me the typical 3-5 seconds cranking until the engine caught and ran, that was 45 mins after I had the car running for 10 seconds to test the check valve's fuel injection clamps for leaking.

Oh well, Eddie will correct it permanently soon. Now I know that pump is 100% working as it should so the peace of mind is there. We're still utilizing the combo unit for the Megasquirt 3.0 system, so I wanted to know it is working perfectly before sending the car to him.

[Silverbullet]

Installed mine today. Looks great! Put electrical tape on the clamps to keep the return hose safe from the sharp corners of the injection clamps.

22121

22122

Didn't fix my cold start issue - was on the fence about it. Fired up absolutely flawlessly after sitting a week. Gave me the typical 3-5 seconds cranking until the engine caught and ran, that was 45 mins after I had the car running for 10 seconds to test the check valve's fuel injection clamps for leaking.

Oh well, Eddie will correct it permanently soon. Now I know that pump is 100% working as it should so the peace of mind is there. We're still utilizing the combo unit for the Megasquirt 3.0 system, so I wanted to know it is working perfectly before sending the car to him.

What is the new RED Wire all about???
Craig

[DeLorean03]

What is the new RED Wire all about???
Craig

The red wire is 12 gauge wire ran from the RPM relay to the fuel pump with a 20A inline fuse. Got tired of fuse #7 melting down, so I introduced what I call "Fuse 7A." I run a power wire straight from the battery to the RPM relay, and then another wire from the RPM relay to the fuel pump.

Here is the post and link documenting the vast majority of the work - read up on the rest of the thread in the link here:

http://dmctalk.org/showthread.php?5911-Dedicated-fuel-pump-circuit&p=84928&viewfull=1#post84928

So far, Fuse #7 has been cold/to mildly warm (maybe a 3 to 4 on a 1-10 scale of arctic cold to hell fire). It NEVER gets hot now - a lil' warm, yes - but hot = not at all anymore.

[NightFlyer]

My review and installation of the SMC 410 check valve from US Plastics Corp, including photos, can be viewed at DMCToday.com for those interested:

http://www.dmctoday.com/showthread.php?276-K-Jet-DMCH-Fuel-Pump-Sender-Combo-External-Inline-Check-Valves&p=3911&viewfull=1#post3911

[Bitsyncmaster]

The red wire is 12 gauge wire ran from the RPM relay to the fuel pump with a 20A inline fuse. Got tired of fuse #7 melting down, so I introduced what I call "Fuse 7A." I run a power wire straight from the battery to the RPM relay, and then another wire from the RPM relay to the fuel pump.

Here is the post and link documenting the vast majority of the work - read up on the rest of the thread in the link here:

http://dmctalk.org/showthread.php?5911-Dedicated-fuel-pump-circuit&p=84928&viewfull=1#post84928

So far, Fuse #7 has been cold/to mildly warm (maybe a 3 to 4 on a 1-10 scale of arctic cold to hell fire). It NEVER gets hot now - a lil' warm, yes - but hot = not at all anymore.

A 20 amp fuse should not even feel warm if your pump has the normal 7 amp draw. The relay compartment does get warm if you have the cover on it for a long drive. So is that what you feel (cover was on)? Can you measure the current draw?

[DeLorean03]

A 20 amp fuse should not even feel warm if your pump has the normal 7 amp draw. The relay compartment does get warm if you have the cover on it for a long drive. So is that what you feel (cover was on)? Can you measure the current draw?

I meant fuse #7. Not Fuse #7A. Fuse #7A is stone cold.

[Bitsyncmaster]

I meant fuse #7. Not Fuse #7A. Fuse #7A is stone cold.

Good:hihi:

[NightFlyer]

For those interested, I stopped and restarted the car about 6 times today, post external in-line check valve installation, over roughly 160 miles of travel, 5 of which were hot starts, and experienced no starting problems to speak of!

Thus I'm DEFINITELY thinking that the combo unit's internal check valve FAILED (or is possibly just insufficient for the back pressures required by a stock/OEM system) - and keep in mind that according to DMCH, I have the revised combo unit that shouldn't be exhibiting any check valve issues.

This is why I personally recommend adding an external in-line check valve with every installation of the combo unit, regardless of what DMCH says about it. DPI is already doing this to all cars that show up for service with the combo unit installed. And as far as external in-line check valves go for our stock/OEM fuel systems, the best choice is the SMC 410 series solid brass with integrated 5/16" barbs, 302 grade stainless steel internals, and a viton seal. Cracking pressure is 1psi and it will hold a back-pressure up to 500psi, thus not only will it get the job done, but it should last a lifetime as well.

The valve is manufactured by SMC - Specialty Manufacturing Co. out of the metro Twin Cities area of Minnesota.

http://www.specialtymfg.com/

US Plastics Corp, of Lima, Ohio, is the retailer that had the best price on the valve at the time of my purchase/recommendation.

USPC also offers shipping via USPS Priority Mail for the same price (or cheaper) than regular ground. Thus, a purchase of the SMC 410 valve supports American workers at every level of the supply chain from manufacturing to delivery! Again, my total, including shipping, came to $17.46.

http://www.usplastic.com/catalog/item.aspx?itemid=85394

Anyone who would even consider purchasing any of the other external in-line check valves is out of their mind IMHO :tongue2:

[Silverbullet]

For those interested, I stopped and restarted the car about 6 times today, post external in-line check valve installation, over roughly 160 miles of travel, 5 of which were hot starts, and experienced no starting problems to speak of!

Thus I'm DEFINITELY thinking that the combo unit's internal check valve FAILED (or is possibly just insufficient for the back pressures required by a stock/OEM system) - and keep in mind that according to DMCH, I have the revised combo unit that shouldn't be exhibiting any check valve issues.

This is why I personally recommend adding an external in-line check valve with every installation of the combo unit, regardless of what DMCH says about it. DPI is already doing this to all cars that show up for service with the combo unit installed. And as far as external in-line check valves go for our stock/OEM fuel systems, the best choice is the SMC 410 series solid brass with integrated 5/16" barbs, 302 grade stainless steel internals, and a viton seal. Cracking pressure is 1psi and it will hold a back-pressure up to 500psi, thus not only will it get the job done, but it should last a lifetime as well.

The valve is manufactured by SMC - Specialty Manufacturing Co. out of the metro Twin Cities area of Minnesota.

http://www.specialtymfg.com/

US Plastics Corp, of Lima, Ohio, is the retailer that had the best price on the valve at the time of my purchase/recommendation.

USPC also offers shipping via USPS Priority Mail for the same price (or cheaper) than regular ground. Thus, a purchase of the SMC 410 valve supports American workers at every level of the supply chain from manufacturing to delivery! Again, my total, including shipping, came to $17.46.

http://www.usplastic.com/catalog/item.aspx?itemid=85394

Anyone who would even consider purchasing any of the other external in-line check valves is out of their mind IMHO :tongue2:

FYI it is STILL "This item is currently unavailable" Does not matter how good it is, if you can't get one...

Craig

[cybercusp]

FYI it is STILL "This item is currently unavailable" Does not matter how good it is, if you can't get one...

Craig

Agreed. I'm still having good luck with the SUR & R valve. Although more expensive I was able to get one very quickly. Incidentally, a quick phone call to SUR&R (1.800.390.3996 (available 8:00 a.m. - 5:00 p.m., U.S. Eastern Standard Time) verified that they are made in the USA.

[DeLorean03]

FYI it is STILL "This item is currently unavailable" Does not matter how good it is, if you can't get one...

Craig

That's why he and others have listed multiple other alternatives. Besides, it's only been a week - give the company time to restock. It's probably a "weird lil' item" to suddenly go "out of stock" on.

[kings1527]

I should probably read through this thread in its entirety once again but I think I'm having more of a cold start issue with the new pump/sender unit. I know my entire cold start system is working 100% and I do have Dave McKeen's RPM relay which primes the fuel system for one second just before startup. I usually don't have a hot start problem that I've realized.

There are times where I'll start my car and it fires up just fine when it's cold. Other times, it takes about 3-4 cranks at about 5 seconds each. It acts exactly like a fuel problem...kind of like when you go to start the car up right after putting the intake manifold back on. It's a bit hard to start, finally catches, sputters a bit for around 5 seconds, and then all's well. For me, I can only imagine that there are times where the check valve functions correctly and other times where it sticks open. And it makes sense: if the valve sticks open, the entire fuel loop would be open and it would be difficult for even the upgraded RPM relay to prime the system and develop enough fuel pressure at the injectors. Almost like the system would backfeed if the check valve were open, if I'm correctly understanding the system design.

I'm guessing the check valve would solve the problem and it looks like they might've just gotten them back in stock. I just ordered one off the website even though it says they're not in stock. I had called them earlier today and the girl on the phone told me they should be in stock in about a week or so, but then later in the day there was the option to order one on the website. So we'll see!

[NightFlyer]

Sounds similar to the problem that DeLorean03 was having with his car, other than the sputtering once it catches. Unfortunately, the addition of the external inline check valve didn't help his problem any.

However, I've experienced the sputtering around issue prior to my installation of the external inline check valve, during both cold and hot starts. Although the sputtering wasn't consistent, when it would occur on my car, I'd have to play with the gas pedal to prevent the car from stalling out before a normal idle finally kicked-in.

Since installing the check valve, roughly 700 miles ago, I haven't experienced the sputtering around problem once, thus it appears to have solved that issue for me. I also haven't had a single hot start issue since installing the valve. Thus I've concluded that even though my pump sender combo unit shouldn't have had the faulty check valve, as according to DMCH my unit came from their revised batch of a different design, it most certainly did have a bad check valve.

It's also Dave M.'s (Bitsyncmaster) and mine theory that the internal check valves in the pump/sender combo unit aren't rated to hold the kind of back-pressures that our fuel system require, as it was probably originally designed for a standard EFI system that operates at around 50psi. So while some may have lucked out with their units for now and into the near future, I honestly don't see any of the internal check valves on any of the combo units lasting longer than 4 years.

Best of luck!

[kings1527]

Sounds similar to the problem that DeLorean03 was having with his car, other than the sputtering once it catches. Unfortunately, the addition of the external inline check valve didn't help his problem any.

However, I've experienced the sputtering around issue prior to my installation of the external inline check valve, during both cold and hot starts. Although the sputtering wasn't consistent, when it would occur on my car, I'd have to play with the gas pedal to prevent the car from stalling out before a normal idle finally kicked-in.


Thanks Josh. My problem definitely sounds like the same one that you were having and it only started about a few hundred miles after I installed the new pump/sender unit. At times, I have to do the exact same thing with the gas pedal. And the more I think about it, the likely I've been also experiencing a hot start issue but just didn't realize it. There must've been a few times when my coolant temp wasn't less than 95 degrees, so it was difficult to start without an extra shot of fuel from the cold start system. For me, the problem is less likely to happen during cold starts. I'm not sure what else it could be, particularly with Dave's RPM relay and its priming feature. I never had a SINGLE issue like this up until I added the new pump/sender.

And don't get me wrong. I love the new design (taking out the screen and pickup tube), the new fuel sender (and an awesome fuel gauge), etc. If all it takes is $20 worth of parts to get everything back in order for an indefinite amount of time, then I'm fine with that. And I'm hearing it might become standard practice to include an external check valve as a precaution with the new units. I think that'd be a good thing to do.

I'll let you know what I find out! Thanks again for your research on the CV and thanks to Michael for getting this very useful thread going!

[DeLorean03]

I am considering re-installing John's power pump setup and seeing what happens. I'm getting a bit tired of this situation. I will prolly do that over the weekend and let everyone know my status if it changes anything.

[NightFlyer]

I am considering re-installing John's power pump setup and seeing what happens. I'm getting a bit tired of this situation. I will prolly do that over the weekend and let everyone know my status if it changes anything.

Hmm... these results just may prove interesting.

[DeLorean03]

We'll see what happens. I want to know once and for all if it is either the pump or the cold start system. Drove the car here to work tonight so I won't be testing the cold start system for at least 2 days. With that being said, I'm more than ready to swap the pumps first and see what happens.

On that note, does anyone know the size of the threads for that threaded stud inside the fuel tank?

[Bitsyncmaster]

If the pump check valve did stick open, that would be a problem but it could be something in the CSV circuit that is not working for cold starts. There are a lot of wire connections in that CSV circuit and that increased the chance for problems with it. My car had a bad bulkhead connection when I got it so the CSV never worked. It's a tough circuit to trace since it does not match the circuit in the schematic. There is a jumper on the back side of two bulkhead connectors that was used to make one of the connections. Wire colors were also not matching. I had to unwrap the harness to trace the circuit.

What I have found:
My car can be parked up to 4 to 6 days in the summer and it will not need the CSV to start it. Longer parked times will need the CSV to get it started. My guess is the injector lines leak down after 6 days. In the very cold winter, most always it will use the CSV to get it started.

How I know when the CSV is used:
I don't have the thermal time switch (TTS) wired into my engine. So if my engine cranks for one second, my hot start relay activates the CSV. It's easy to know that one second of cranking with no engine fire.

[DeLorean03]

Ever since I did my water pump/VOD touch up, this has been the case. Problem is, I introduced the new DMCH combo at nearly the exact same time, so it's always been a "is it this one or that one?" problem for me. What I have noticed is if I unhook my CSV, my car starts MUCH more easily. Today with the CSV hooked up after a 10 hour overnight shift, my car nearly didn't start in the parking lot. I haven't done this level of diagnosis with John's pump - hence - my desire to try it.

[jawn101]

This may not be the right thread to ask this in, but I'm hoping it will reach a lot of people who have the unit by posting it here. I've been having an issue with mine pretty consistently since I installed it where if the gauge drops below about 1/4 tank, I start getting the same sputtering symptoms I used to have with the OEM setup and a collapsing pickup hose.

It happened today on the way home from an event - 260 miles on the clock, a hair below 1/4 on the gauge and I got on the throttle to merge onto the freeway and bam - bucking and shuddering. Pulled off at the next exit and filled up - the tank took 11 gallons. So the gauge is pretty accurate - it goes precisely to the 4/4 mark when full - but what's the deal with the delivery at 1/4 tank? Symptoms were totally gone after the fillup and only occur when the tank is "low"

It is also worth mentioning that I've got a few thousand miles and a couple months on the pump and haven't had any issues with the check valve - hopefully it stays that way.

[NightFlyer]

This may not be the right thread to ask this in, but I'm hoping it will reach a lot of people who have the unit by posting it here. I've been having an issue with mine pretty consistently since I installed it where if the gauge drops below about 1/4 tank, I start getting the same sputtering symptoms I used to have with the OEM setup and a collapsing pickup hose.

It happened today on the way home from an event - 260 miles on the clock, a hair below 1/4 on the gauge and I got on the throttle to merge onto the freeway and bam - bucking and shuddering. Pulled off at the next exit and filled up - the tank took 11 gallons. So the gauge is pretty accurate - it goes precisely to the 4/4 mark when full - but what's the deal with the delivery at 1/4 tank? Symptoms were totally gone after the fillup and only occur when the tank is "low"

It is also worth mentioning that I've got a few thousand miles and a couple months on the pump and haven't had any issues with the check valve - hopefully it stays that way.

1) PLEASE - install an external inline check valve. Trust me, you'll be glad that you did. It's $18 and all of 20 minutes of time. It's definitely worth it IMHO!

2) When you installed the pump, are you sure that you had the bottom of the pump as close to touching the bottom of the tank as possible? The unit, as you probably know, is spring loaded and isn't very smooth in it's action when decompressing after being compressed (it's easy to get it stuck in a compressed state). It also doesn't fit the tank when fully decompressed, thus some level of compression is necessary. I test fit mine about 4 times before I was able to get it where the bottom of the pump was just barely off the bottom of the tank. I've only been running mine for the last 3 months and about 4,000 miles, but have always run it down low enough to trip the low fuel light. No issues such as those you've described thus far.

That's about the only thing that I can think of.

You may also want to check the RPM relay - if that's opening/closing while you're driving, it could potentially cause what you're describing as it's stopping and re-engaging the pump.

Best of luck!

[jawn101]

1) PLEASE - install an external inline check valve. Trust me, you'll be glad that you did. It's $18 and all of 20 minutes of time. It's definitely worth it IMHO!

2) When you installed the pump, are you sure that you had the bottom of the pump as close to touching the bottom of the tank as possible? The unit, as you probably know, is spring loaded and isn't very smooth in it's action when decompressing after being compressed (it's easy to get it stuck in a compressed state). It also doesn't fit the tank when fully decompressed, thus some level of compression is necessary. I test fit mine about 4 times before I was able to get it where the bottom of the pump was just barely off the bottom of the tank. I've only been running mine for the last 3 months and about 4,000 miles, but have always run it down low enough to trip the low fuel light. No issues such as those you've described thus far.

That's about the only thing that I can think of.

You may also want to check the RPM relay - if that's opening/closing while you're driving, it could potentially cause what you're describing as it's stopping and re-engaging the pump.

Best of luck!

Yes, an external check valve is on the list for the rainy season when it starts in a month or so. Peace of mind is worth everything to me.

I don't actually know for sure about the pump being compressed fully. That might be a factor, but would the gauge be off if it wasn't fully compressed in the tank? Or is the float attached at the top? I can't remember.

RPM relay is already Dave's solid state one and works fine under all circumstances - this issue only crops up when the tank drops low-ish.

[NightFlyer]

Yes, an external check valve is on the list for the rainy season when it starts in a month or so. Peace of mind is worth everything to me.

I don't actually know for sure about the pump being compressed fully. That might be a factor, but would the gauge be off if it wasn't fully compressed in the tank? Or is the float attached at the top? I can't remember.

RPM relay is already Dave's solid state one and works fine under all circumstances - this issue only crops up when the tank drops low-ish.

If I'm recalling correctly, the float is attached near the middle of the pump body. However, the arm is long and contains a near 90 degree bend, thus allowing it to extend above the top and below the bottom of the pump. So, the float will still read properly even if the pump is over-compressed in the installation.

Remember, you want the pump as fully DE-compressed as possible in the installation.

[NightFlyer]

If I'm recalling correctly, the float is attached near the middle of the pump body. However, the arm is long and contains a near 90 degree bend, thus allowing it to extend above the top and below the bottom of the pump. So, the float will still read properly even if the pump is over-compressed in the installation.

Remember, you want the pump as fully DE-compressed as possible in the installation.

OK, the mount/pivot point is actually towards the top, but the angle of the rod is a full 90 degrees. Recalling my pump, I distinctly remember the float bottoming just slightly below the bottom of the pump.

I'd also check for cracks in the plastic housing - maybe air is being introduced that way...???

https://store.delorean.com/images/Product/large/10569.jpg

[jawn101]

OK, the mount/pivot point is actually towards the top, but the angle of the rod is a full 90 degrees. Recalling my pump, I distinctly remember the float bottoming just slightly below the bottom of the pump.

I'd also check for cracks in the plastic housing - maybe air is being introduced that way...???

https://store.delorean.com/images/Product/large/10569.jpg

Interesting. So I should remove the pump assembly and make sure it's fully extended to the bottom of the tank. That makes sense, but I'm not looking forward to it. Maybe I'll do it when I splice in that check valve.

[NightFlyer]

I am considering re-installing John's power pump setup and seeing what happens. I'm getting a bit tired of this situation. I will prolly do that over the weekend and let everyone know my status if it changes anything.

I'm curious as to whether or not you tried this yet, and if so, what the results were...

[andy blackmon]

Today I installed the check valve in my fuel line. I had an on and off hot start issue and I figured what the heck the valve can't hurt. For anyone on the fence with this, hey the cost was around $15 and it took me around 15 minutes to put it in.
Andy B 03513

[DeLorean03]

I'm curious as to whether or not you tried this yet, and if so, what the results were...

Didn't get to it. Here's why. I have unhooked my CSV, and ever since then, my car fires nearly flawlessly all the time. It's something in the cold start system, and since Eddie is about to fix that permanently, I said "heck with it".

Car heads to him a week from Monday, and it's 55 here for the high, so yeah, the days of driving the DeLorean for 2013 are pretty much over.

[kings1527]

Ok, so I got mine taken care of. I TRIED to order the Viton check valve from US Plastics and it was taking FOREVER to them to get them back in stock. So I went with the same check valve but with Buna-N instead since they had those. And of course, about 3 days after I order the Buna-N, they get the Viton back in stock. :facepalm:

So I installed it and yes, super easy to do. But I still had my hot start problem. After researching it, I know that lack of rest pressure is really only due to three things under most circumstances:

1) Fuel pump check valve
2) Accumulator
3) PPR O-Rings

Since the PPR O-rings were the path of least resistance at this point, I went there first. I had some that I bought from Hervey :nervous: about 6 months ago and put them in last night. Another 15 min job, if that. I was a little nervous when I got the old o-rings out because there wasn't anything obviously wrong with them. Once I took the old small o-ring off and put it next to the new small o-ring, the old one was noticeably larger than the new one. That was the only difference. But Hervey's new o-rings were a perfect, snug fit (thankfully and with intense relief) and I didn't have any problems getting them back in and damaging them along the way. I put a very light coat of silicone paste on the o-rings to help facilitate sliding everything back in, just in case.

And that was it. The DeLorean starts up just as fast as my 2013 Passat, whether hot or cold.

Doc Brown in reference to the PPR O-rings: "Unbelievable that this little piece of junk could be such a big problem".


Thanks for the help!

[opethmike]

Yes, you definitely have to use lubricant before sliding in.

[Bitsyncmaster]

Buna-N will swell with todays gas. Look at that O-ring after it sits out on the bench awhile. It should get smaller. I did a swell test measurement back on the old .com forum but don't have a copy of my results.

[kings1527]

Buna-N will swell with todays gas. Look at that O-ring after it sits out on the bench awhile. It should get smaller. I did a swell test measurement back on the old .com forum but don't have a copy of my results.

Interesting. That might be why my old o-ring was noticeably larger. I did a lot of research on the material and it said it was compatible with gasoline. What other applications would Buna-N be used for?

I still have a Viton check valve on the way so I'll probably just swap it out and be done with it. Any idea how long it takes for Buna-N to deform?

Who has a good source for Viton o-rings for the PPR?

[Tillsy]

Yes, you definitely have to use lubricant before sliding in.

Yep, that's what she said...

[Bitsyncmaster]

Interesting. That might be why my old o-ring was noticeably larger. I did a lot of research on the material and it said it was compatible with gasoline. What other applications would Buna-N be used for?

I still have a Viton check valve on the way so I'll probably just swap it out and be done with it. Any idea how long it takes for Buna-N to deform?

Who has a good source for Viton o-rings for the PPR?

This is where I get mine:
http://www.mcmaster.com/#metric-o-rings/=p3nifs

I use 1.9 mm X 3.8 mm but I think the stock size is 2.0 mm X 4.0 mm. Either works but I guess the smaller one gets more seal since it has less surface area. Viton is a little harder then Buna-N.

[DMC5180]

This is where I get mine:
http://www.mcmaster.com/#metric-o-rings/=p3nifs

I use 1.9 mm X 3.8 mm but I think the stock size is 2.0 mm X 4.0 mm. Either works but I guess the smaller one gets more seal since it has less surface area. Viton is a little harder then Buna-N.

I fail to see how a smaller one gets MORE seal with LESS surface area. :hmm:

[Bitsyncmaster]

I fail to see how a smaller one gets MORE seal with LESS surface area. :hmm:

Constant pressure to less surface area will compress the o-ring more than a larger surface area.

[kings1527]

This is where I get mine:
http://www.mcmaster.com/#metric-o-rings/=p3nifs

I use 1.9 mm X 3.8 mm but I think the stock size is 2.0 mm X 4.0 mm. Either works but I guess the smaller one gets more seal since it has less surface area. Viton is a little harder then Buna-N.

Thanks perfect, thanks for the info Dave. So that'll be the size for the smaller o-ring. Do we know the size for the bigger o-ring? Or does that one prove to not be much of a factor for holding rest pressure when compared to the smaller o-ring?

[Bitsyncmaster]

Thanks perfect, thanks for the info Dave. So that'll be the size for the smaller o-ring. Do we know the size for the bigger o-ring? Or does that one prove to not be much of a factor for holding rest pressure when compared to the smaller o-ring?

Don't worry about the larger O-ring. It really stays dry and does not need to seal.

[NightFlyer]

Ok, so I got mine taken care of. I TRIED to order the Viton check valve from US Plastics and it was taking FOREVER to them to get them back in stock. So I went with the same check valve but with Buna-N instead since they had those. And of course, about 3 days after I order the Buna-N, they get the Viton back in stock. :facepalm:

So I installed it and yes, super easy to do. But I still had my hot start problem. After researching it, I know that lack of rest pressure is really only due to three things under most circumstances:

1) Fuel pump check valve
2) Accumulator
3) PPR O-Rings

Since the PPR O-rings were the path of least resistance at this point, I went there first. I had some that I bought from Hervey :nervous: about 6 months ago and put them in last night. Another 15 min job, if that. I was a little nervous when I got the old o-rings out because there wasn't anything obviously wrong with them. Once I took the old small o-ring off and put it next to the new small o-ring, the old one was noticeably larger than the new one. That was the only difference. But Hervey's new o-rings were a perfect, snug fit (thankfully and with intense relief) and I didn't have any problems getting them back in and damaging them along the way. I put a very light coat of silicone paste on the o-rings to help facilitate sliding everything back in, just in case.

And that was it. The DeLorean starts up just as fast as my 2013 Passat, whether hot or cold.

Doc Brown in reference to the PPR O-rings: "Unbelievable that this little piece of junk could be such a big problem".


Thanks for the help!

Glad to hear that you were finally able to figure out the problem! It's great to finally have a car that you know will start every time, isn't it?

[kings1527]

Don't worry about the larger O-ring. It really stays dry and does not need to seal.

Great, thanks Dave.


Glad to hear that you were finally able to figure out the problem! It's great to finally have a car that you know will start every time, isn't it?

There's hardly anything worse than trying to start the car and nothing's happening! And it always happens in front of a group of people. Then you're just waiting for the jokes to start flying.... :)

It'll be nice to get the Viton check valve and PPR o-ring in place and be done!

[kings1527]

So for anyone who's interested, it's been about two months since I put a regular (assuming) Buna-N o-ring in my PPR plunger and my car just started doing the same thing as I described earlier. So I guess one could say the average life span before Buna-N will deform is about two months. Dastardly ethanol.

Today I installed the nitrile o-ring with the size Dave M mentioned and I'll report back if there are any problems. If I pass the two month mark, I'll take it as a good sign.

[rdarlington]

What were the original o-rings made out of? Mine is original and I pump the cheapest gas I can find. Buna rubber o-rings are considered to have excellent compatibility with ethanol for both static and dynamic applications. Basically, the same compatibility as viton.

-Bob

[kings1527]

My terminology is mixed up. You're right. Viton (not nitrile) is the stuff that's been widely regarded in the forum to have the best compatibility with ethanol. Buna-N supposedly still has problems. As to what the originals were made of, I'm not sure but I'm guessing they held up better back in the day due to the fact that ethanol hadn't been introduced yet.

[NightFlyer]

Buna-N is NOT ethanol resistant - it will deteriorate when exposed to ethanol of any concentration - higher concentrations will cause faster wear.

Viton has been independently tested to be impervious to ethanol concentrations as high as 15%, although DuPont claims it can handle much higher concentrations without issue.

[rdarlington]

Buna-N is absolutely compatible with ethanol, in concentrations as high as they get (don't get me started on azeotropes).

Every o-ring manufacturer out there lists this and Buna-N (nitrile) is the recommended material for sealing with o-rings for ethanol.

[rdarlington]

Actually from what I'm reading, Viton is actually a poor choice for ethanol. It's marginal at best.

Simply put, if Buna-N o-rings are deteriorating because of modern fuels, it is most definitely NOT because of the ethanol in them.

-Bob

[Bitsyncmaster]

It's a good question about original O-rings. My guess is they are Buna-N but maybe were a smaller size. I tested Buna and Viton side by side soaking in ethanol gas. The Buna expanded quite a bit and the Viton did not change at all. So if my guess is correct, the smaller size keeps Buna-N working.

[kings1527]

Actually from what I'm reading, Viton is actually a poor choice for ethanol. It's marginal at best.

Simply put, if Buna-N o-rings are deteriorating because of modern fuels, it is most definitely NOT because of the ethanol in them.

-Bob

Not sure where you're reading about Viton being a poor choice for ethanol but that's not right. It's not so much a matter of deterioration, but rather swelling resulting in deformity. That's why the PPR o-ring starts having problems. It becomes malformed and can't hold rest pressure. I've personally (as have others) seen a nice swollen buna-n o-ring from ethanol based fuel.

In short, go with Viton unless you want to look cool working on your car all the time.

And a special thanks to Dave M for all of his research and info on this.

[rdarlington]

Not sure where you're reading about Viton being a poor choice for ethanol but that's not right. It's not so much a matter of deterioration, but rather swelling resulting in deformity. That's why the PPR o-ring starts having problems. It becomes malformed and can't hold rest pressure. I've personally (as have others) seen a nice swollen buna-n o-ring from ethanol based fuel.

In short, go with Viton unless you want to look cool working on your car all the time.

http://www.sterlitech.com/oring-compatibility-chart


I see viton listed all over the map for both gasoline and ethanol.

One thing I see that's consistent is Buna-N for both gasoline and ethanol resistance. It is *the* recommended material for both. Who is manufacturing your o-rings? Are you sure you're getting what you're paying for?

Just an FYI, I have extensive experience in the vacuum technology and industrial chemistry world and deal with chemical compatibility for these types of seals for both terrestrial and space applications. What I think is that you guys are picking up 3rd rate o-rings and are making assumptions. The available data out there from the manufacturers and industry publications suggest that Buna-N is the stuff you want for o-rings for cars. They've been using ethanol in gasoline since the 1920s (granted, the o-ring didn't exist in the 1920s) and is not new.

There are plenty of reasons to go with viton, but I don't think I know of any where it comes to dealing with cars.

-Bob

[NightFlyer]

Deteriorate wasn't the best word to use - should have been 'compromised' instead.

Whether it's being caused by the ethanol or something else, fact remains that Buna-N is compromised by today's standard fuel blends, whereas Viton is not. Dave M's side by side is consistent with the results of other comparison tests that I've seen. Alex's recent personal experience would also seem to validate/support the concerns about using Buna-N in applications on our cars.

While the choice is yours to make, I can personally attest to the fact that I haven't encountered any issues running Viton rubber in the fuel system components on my car.

The difference in price between the two materials is marginal/nominal at best...

[Bitsyncmaster]

It only takes about a one or two hour soak in gasohol if you have some calipers to do the test I did.

Measure each before you soak, Tag which is which, soak and remeasure. I would like another verify of what you find.

[David T]

It only takes about a one or two hour soak in gasohol if you have some calipers to do the test I did.

Measure each before you soak, Tag which is which, soak and remeasure. I would like another verify of what you find.


The problem is we really do not know exactly what the originals were made of. What they sell today and call Buna N is probably not what they used to make. Whatever the originals were made of, it seemed to be OK. The problems seem to start once you change them. There are plenty of mixture units out there with the original "O" rings in them and they function just fine. If you should replace them I would suggest you try to use Viton of the correct size since what they pass off as Buna N is not going to work. I believe one of the problems is that the Buna N swells and since this is a dynamic seal (the "O" rings are on parts that move) when it swells it gets chopped as it moves over the slots. If it was just used to seal a part that doesn't move (like a drain plug) where it is captured and cannot swell, Buna N seems to be fine.

[Ron]

There are plenty of reasons to go with viton, but I don't think I know of any where it comes to dealing with cars.
...Automatic transmission o-rings and seals.

...I used a Viton o-ring from rebuilt kit leftovers and have had no problems for years.
Back when Dave first posted measurement/results, I had very similar results.

[jawn101]

1) PLEASE - install an external inline check valve. Trust me, you'll be glad that you did. It's $18 and all of 20 minutes of time. It's definitely worth it IMHO!

2) When you installed the pump, are you sure that you had the bottom of the pump as close to touching the bottom of the tank as possible? The unit, as you probably know, is spring loaded and isn't very smooth in it's action when decompressing after being compressed (it's easy to get it stuck in a compressed state). It also doesn't fit the tank when fully decompressed, thus some level of compression is necessary. I test fit mine about 4 times before I was able to get it where the bottom of the pump was just barely off the bottom of the tank. I've only been running mine for the last 3 months and about 4,000 miles, but have always run it down low enough to trip the low fuel light. No issues such as those you've described thus far.

That's about the only thing that I can think of.

You may also want to check the RPM relay - if that's opening/closing while you're driving, it could potentially cause what you're describing as it's stopping and re-engaging the pump.

Best of luck!

Hey - this is a little late for a follow up, but that's how long it took me to run the fuel tank down low enough to inspect. I just pulled the blanking plug off the level sender hole and inspected the pump. It is fully extended and resting on the bottom of the tank. There is about 1/4" of fuel surrounding the baffle area (that is to say that the baffle is about 1/4" submerged) and the gauge is reading a tick below 1/4 full. But I still have the "collapsed pickup hose" symptoms under hard acceleration when the tank is this low.

Anyone have any other ideas what could be causing this? Dave S, are you still out there reading this thread? :)

[NightFlyer]

Hey - this is a little late for a follow up, but that's how long it took me to run the fuel tank down low enough to inspect. I just pulled the blanking plug off the level sender hole and inspected the pump. It is fully extended and resting on the bottom of the tank. There is about 1/4" of fuel surrounding the baffle area (that is to say that the baffle is about 1/4" submerged) and the gauge is reading a tick below 1/4 full. But I still have the "collapsed pickup hose" symptoms under hard acceleration when the tank is this low.

Anyone have any other ideas what could be causing this? Dave S, are you still out there reading this thread? :)

Sounds like a crack somewhere within the assembly is introducing air into the system when the fuel level gets low enough. Is the pump still under warranty?

[jawn101]

Sounds like a crack somewhere within the assembly is introducing air into the system when the fuel level gets low enough. Is the pump still under warranty?

Probably not. I'd have to pull the whole assembly to check for one.

FWIW, I did measure the fuel levels in the tank and it seems like there is more around 1" of fuel down there. Perspective made it tough to estimate properly, and I had a hard time getting a real measurement as the fuel mostly evaporated off my rulers before I could get them into the light to read.

[NightFlyer]

Probably not. I'd have to pull the whole assembly to check for one.

FWIW, I did measure the fuel levels in the tank and it seems like there is more around 1" of fuel down there. Perspective made it tough to estimate properly, and I had a hard time getting a real measurement as the fuel mostly evaporated off my rulers before I could get them into the light to read.

I would think that an inch should be enough fuel to still operate the pump normally, but then again, I really don't have any basis of comparison / experience. It's possible that the sender float is incorrectly adjusted and giving an incorrect reading on the dash gauge.

One way to check would be to siphon the remaining fuel in the tank into something that you can use to measure the amount of fuel actually present and compare it to what the gauge is reporting. You can siphon via the sender hole. Inclining the car (by parking on a steep incline or jacking it up) will concentrate the remaining fuel into either the front or back of the tank where you can effectively siphon a vast majority of the remaining fuel out (only a nominal/insignificant amount will remain). Remember that the tank's capacity is 13.2 gallons, thus if your gauge is reading 1/4 tank, you should have roughly 3.3 gallons of fuel remaining within the tank. If the gauge is close to what your measured results yield, then you'll know for certain that the problem lies in the pump housing, unfortunately...

Again, best of luck!

[David T]

I would think that an inch should be enough fuel to still operate the pump normally, but then again, I really don't have any basis of comparison / experience. It's possible that the sender float is incorrectly adjusted and giving an incorrect reading on the dash gauge.

One way to check would be to siphon the remaining fuel in the tank into something that you can use to measure the amount of fuel actually present and compare it to what the gauge is reporting. You can siphon via the sender hole. Inclining the car (by parking on a steep incline or jacking it up) will concentrate the remaining fuel into either the front or back of the tank where you can effectively siphon a vast majority of the remaining fuel out (only a nominal/insignificant amount will remain). Remember that the tank's capacity is 13.2 gallons, thus if your gauge is reading 1/4 tank, you should have roughly 3.3 gallons of fuel remaining within the tank. If the gauge is close to what your measured results yield, then you'll know for certain that the problem lies in the pump housing, unfortunately...

Again, best of luck!

You really cannot properly inspect the baffle assembly from the sender unit hole. Pull the pump out and inspect the pick-up hose. If is is swollen or soft either put a spring in it or replace it.

[DMC5180]

You really cannot properly inspect the baffle assembly from the sender unit hole. Pull the pump out and inspect the pick-up hose. If is is swollen or soft either put a spring in it or replace it.


David,

Jon has the NEW DMCH Pump combo unit. No Pickup hose on this one.

[jawn101]

OK, after trading some emails, photos, videos and some call time with Dave S (have I mentioned lately how great he is?) I've got a plan of action.

First step was to test the level sender. I held the float down gently with this threaded rod:

http://dmctalk.org/attachment.php?attachmentid=24648&d=1390256908

Then verified that the sender and low fuel light were working properly

http://dmctalk.org/attachment.php?attachmentid=24649&d=1390256911

OK, that's all fine. On to the next step - running the engine with the sender plug removed to observe the pump operation.


https://www.youtube.com/watch?v=ACfkTwB4AJc

Um. Well, I'm pretty sure that isn't supposed to happen. Next step was to remove and inspect the pump assembly for leaks/cracks:

http://dmctalk.org/attachment.php?attachmentid=24650&d=1390256918

http://dmctalk.org/attachment.php?attachmentid=24651&d=1390256925

http://dmctalk.org/attachment.php?attachmentid=24652&d=1390256933

http://dmctalk.org/attachment.php?attachmentid=24653&d=1390256939

Clean as a whistle and no obvious cracks/splits or anything concerning. So, I tried reinstalling the assembly. It's a DeLorean after all, sometimes a simple R&R is all it takes to fix a problem, right?

Wrong. Same symptoms after reinstalling. So I pulled the pump up out of the tank just enough to observe it in operation from directly above instead of from the side. Here's what I saw:

https://www.youtube.com/watch?v=3bKBobEnZos (sorry, can only embed 1 video per post for some reason?)

Uh oh. The leak is right at the top of the pump itself.

So right now the working theory is that the pump was still providing adequate pressure to the engine (no issues at all with running or driveability unless the gas is very low) but due to this leak, the fuel in the baffle was being depleted very quickly - causing the poor running conditions with low fuel in the tank.

Long and short of it is that 2100 is off the road while the pump assembly heads back to DMCMW for a thorough check and repair by Dave. A bummer but at least it's a resolution!

Will update again when I have more info on the situation.

BTW: Dave said he was going to return the unit with an inline check valve supplied.

[DavidProehl]

Great job documenting this. That is surprising to see gas leaking out the top of the unit! No wonder it was so hard to track down.

[kings1527]

Sorry to hear about the leak, Jon, but wow...great job troubleshooting this. If it's in Dave's hands now, we all know it's in good hands!

[DeLorean03]

Wow, that was a thorough investigation. Good job on tracking this one down!

[jawn101]

Can't take all the credit, Dave is the man when it comes to this stuff. I just hope he can find and fix whatever the issue is, because I swear there is *nothing* visibly wrong with that pump. I have no idea what's leaking!

Edit: I should say that I'm glad I took the time to dig into what was really just a minor annoyance. It's a good lesson to investigate any and all abnormal behavior in your car - you never know when a minor symptom could be hiding a major problem!

[Ryan S.]

Good job diagnosing the issue. Let us know what Dave finds out.
Mine worked really great after the external check valve. But recently, I have been experiencing some mild random cold start issues. Cannot figure out the cause. It stars fine in the "cold" mornings but when I start in the afternoon or after work, I have to crank it for several seconds. But not always. Some afternoon, it starts fine.

[NightFlyer]

Glad that you were able to get this mystery solved!

Hopefully it's a fluke as opposed to being an endemic problem...

[jawn101]

Glad that you were able to get this mystery solved!

Hopefully it's a fluke as opposed to being an endemic problem...

Thank you. Your advice and responses have been invaluable in tracing the issue as well. I also hope that it's a fluke and not endemic, but realistically how would anyone know without checking? I put the bad unit in the mail to Dave today and can't wait for the triage and AAR on it, and to get the car running again!

[NightFlyer]

Only way to know other than checking would be to run the tank low and see if they experienced the bucking / fuel starvation issues that you did.

I've run my unit for roughly 4 months and about 5,000 miles. Before putting the car away for winter hibernation, I ran the tank down to practically fumes (less than a gallon remaining) before adding a can of seafoam and 5 gallons of ethanol free fuel and driving home, and didn't experience any bucking / fuel starvation problems - knock on wood. I was actually sweating whether I'd make it to the gas station with the e-free fuel before I completely ran out of fuel and would end up having to walk.

So, I presume that thus far, other than having a faulty internal check valve, my unit is operating properly.

[David T]

Didn't know you had the newer unit. They do seem to have as many problems as they are supposed to solve! Between leaks, bad check valves, and the level indicator not being accurate, it would seem you are trading one set of problems for another set! Too bad, it could have been done much better. While it is removed you might as well clean the tank out.The good news is you finally have your hands on the problem.

[jawn101]

Didn't know you had the newer unit. They do seem to have as many problems as they are supposed to solve! Between leaks, bad check valves, and the level indicator not being accurate, it would seem you are trading one set of problems for another set! Too bad, it could have been done much better. While it is removed you might as well clean the tank out.The good news is you finally have your hands on the problem.

The unit does seem to have some teething problems but I don't think I can agree that it's as bad as the original setup.

The tank was sanitized prior to installation of the unit (as required by DMCH for warranty purposes) but you're right - I plan to give it another wipedown while the hole is open all the same. The hope is that nothing was missed the first time but who knows.

[kings1527]

I agree that this setup seems to be a big improvement over the original. I haven't had any issues with my fuel sender not reading correctly on the new unit. And DMCH is now selling the new setup with a brass external check valve (with a price tag now of $419 instead of the original $399). Of all the units that have been sold thus far, this is the only one that I've heard of having this type of a leak.

[jawn101]

I agree that this setup seems to be a big improvement over the original. I haven't had any issues with my fuel sender not reading correctly on the new unit. And DMCH is now selling the new setup with a brass external check valve (with a price tag now of $419 instead of the original $399). Of all the units that have been sold thus far, this is the only one that I've heard of having this type of a leak.

Just my awesome luck... :)

[Ryan S.]

I also cleaned my tank twice between repairs. Mine was very clean. Didn't really have to clean.

[Bitsyncmaster]

So far it seems it fixed the old problem of the pump buzzing when the fuel gets hot. I think that buzzing was causing most pump failures.

[Grover]

Just my awesome luck... :)

I've been using the unit since it first came out. I am on my 4th pump and it seems to be working now (I also installed an in-line check valve). The problem that I have now is that the sender will always read 1/4 tank too high. So when I fill up my gauge is 1/4 past full. This creates an issue since now when the check engine light comes on I have .5 gallons left (ask me how I know, got lucky deciding to fill up).

This has been the case with two pumps so far and can't find the issue. Working on replacing the float arm but can't figure out an easy way to remove it to put the replacement one on. If that doesn't solve the problem I am thinking maybe it is an electrical box issue (the box that came with the unit). I have one of the first ones and it is not sealed, I am thinking maybe it is not reading the resistance correctly from possible moisture entering the box? It shouldn't matter if the float arm is bent or not as the contact point on the swing arm for the gauge should read full no matter what, not push the gauge 1/4 past full.

Has another else run into this problem?

[jawn101]

I also cleaned my tank twice between repairs. Mine was very clean. Didn't really have to clean.

I cleaned my tank again today too, since the whole thing was open and the car is immobile anyway. It was very clean, but I did see one chunk of the old boot that I could grab with my fingers - about 0.5mm around maybe? Unfortunately the second I touched it it turned to dust. So I wiped down the whole freaking thing again - no sense cutting corners!

[DeLorean]

I have the DMCH fuel pump, and I just ordered the usplastic check valve. Now... I can't diss the product, It is nice to have someone selling improved products for these cars, but....... It seems like pretty frequently there is not a whole lot of real world testing of products done by DMCH before they put such things on sale. True to the original manufacturer I guess? I have bought their ball joints, their headlight switch, and now their fuel pump assembly, all of which have proven defective in a time test of actual use.

Now. the headlight switch (so far) has required an uprated fuse to function properly, and the fuel pump (hopefully) will just require this check valve to be reliable, and the ball joints, well... those were just made wrong.

I would love if a new product they intend to sell they would install on a car of theirs for 3 months, drive it 12,000 miles in that time, to verify that they actually FUNCTION properly before they sell them to hundreds of customers, as their test mules.

People who actually drive their D's this stuff just has to work right.

[David T]

I have the DMCH fuel pump, and I just ordered the usplastic check valve. Now... I can't diss the product, It is nice to have someone selling improved products for these cars, but....... It seems like pretty frequently there is not a whole lot of real world testing of products done by DMCH before they put such things on sale. True to the original manufacturer I guess? I have bought their ball joints, their headlight switch, and now their fuel pump assembly, all of which have proven defective in a time test of actual use.

Now. the headlight switch (so far) has required an uprated fuse to function properly, and the fuel pump (hopefully) will just require this check valve to be reliable, and the ball joints, well... those were just made wrong.

I would love if a new product they intend to sell they would install on a car of theirs for 3 months, drive it 12,000 miles in that time, to verify that they actually FUNCTION properly before they sell them to hundreds of customers, as their test mules.

People who actually drive their D's this stuff just has to work right.

DMCH does test their new products but you have to understand that they cannot spend the time and money to run a thorough testing program for all of the possible conditions. That said you still expect better than what history has shown. My guess as to what is happening with the fuel unit is that most of the time you are replacing the old stuff because it got old and cruddy. If you do not COMPLETELY clean the tank spotless, any dirt will just mess up the new parts. Now you start blaming the new parts you put in, not realizing the dirt ruined them. That doesn't explain leaks. Or the inaccurate fuel level indicator.

[Bill6298]

DMCH does test their new products but you have to understand that they cannot spend the time and money to run a thorough testing program for all of the possible conditions. That said you still expect better than what history has shown. My guess as to what is happening with the fuel unit is that most of the time you are replacing the old stuff because it got old and cruddy. If you do not COMPLETELY clean the tank spotless, any dirt will just mess up the new parts. Now you start blaming the new parts you put in, not realizing the dirt ruined them. That doesn't explain leaks. Or the inaccurate fuel level indicator.

David,

Do you think other dirty fuel-related parts could be part of the overall problem? e.g. spotless tank but the return fuel is coming back in contaminated from other K-Jet components.

Bill

[jawn101]

David,

Do you think other dirty fuel-related parts could be part of the overall problem? e.g. spotless tank but the return fuel is coming back in contaminated from other K-Jet components.

Bill

Most people who install the new fuel pump kit have already overhauled the rest of the system, so there should be no contamination to return. New fuel lines are a must in this car at this point. So if your flex lines and filter are new, injectors/WUR/FD are clean, hard lines are flushed, tank is clean and free of 30 year old rubber parts - there should be nothing to come back and gum anything up.

Sounds like your fuel system definitely has a way to go, but don't despair - you'll get there! K-Jet is just incredibly sensitive.

Edit: Not to mention that there shouldn't be anything to decay downstream of the fuel filter in the first place. I'm turning the system over in my head and if anything, the fuel that's returned to the tank should be cleaner than the fuel that left it, barring significant pre-existing contamination.

[David T]

Most people who install the new fuel pump kit have already overhauled the rest of the system, so there should be no contamination to return. New fuel lines are a must in this car at this point. So if your flex lines and filter are new, injectors/WUR/FD are clean, hard lines are flushed, tank is clean and free of 30 year old rubber parts - there should be nothing to come back and gum anything up.

Sounds like your fuel system definitely has a way to go, but don't despair - you'll get there! K-Jet is just incredibly sensitive.

Edit: Not to mention that there shouldn't be anything to decay downstream of the fuel filter in the first place. I'm turning the system over in my head and if anything, the fuel that's returned to the tank should be cleaner than the fuel that left it, barring significant pre-existing contamination.

In my mind I believe most fuel system problems begin in the tank. That is where dirt, stale fuel and water get into the system. In that same light, when you start working on the fuel system the tank is where you begin. Theoretically the filter is supposed to trap any dirt but if you have stale fuel it is already downstream of the filter. There is a filter in the CPR and each injector has a screen but by then it is usually too late. If you find, after cleaning the tank, you are getting dirt and junk back into it, it means the system is contaminated and you are flowing the stuff back to the tank from the fuel lines and PPR. Keep cleaning the tank and eventually it should clean up. If you see a tank full of junk the injectors need to be cleaned.

[jawn101]

So, just as an update - Dave and Houston couldn't figure out what was causing the issue, and apparently the unit is going back to the manufacturer. I have a new one inbound, complete with external check valve. Looking forward to installing it and getting rolling again!

[NightFlyer]

So, just as an update - Dave and Houston couldn't figure out what was causing the issue, and apparently the unit is going back to the manufacturer. I have a new one inbound, complete with external check valve. Looking forward to installing it and getting rolling again!

Good deal - glad to see them standing behind the product! Thanks for keeping us updated :thumbup:

[Ryan S.]

Nice. Post some photos of the new pump. I am curious about the location and type of check valve.

[jawn101]

Nice. Post some photos of the new pump. I am curious about the location and type of check valve.

It's an inline one, as I understand it - the box should arrive Thursday and I doubt I'll be able to stop myself from installing it immediately. Pictures will definitely follow.

[DeLorean]

On a somewhat related note, has anyone done an amp-draw test on the new pumps Vs the old type? My guess would be there is probably a savings of an amp or 2 being that it is a more modern pump rather than an old Bosch roller type pump - true? Might be a bit of help to the fuel pump relay lifespan.

[Bitsyncmaster]

On a somewhat related note, has anyone done an amp-draw test on the new pumps Vs the old type? My guess would be there is probably a savings of an amp or 2 being that it is a more modern pump rather than an old Bosch roller type pump - true? Might be a bit of help to the fuel pump relay lifespan.

Something I would like to know also. If you test the current, do it with the engine running so you have a normal voltage.

[David T]

Something I would like to know also. If you test the current, do it with the engine running so you have a normal voltage.

The best test would be on a car with a nice, clean, well working electrical system. Getting a # off of a car with dirty connections, an old pump, and bad grounds won't mean anything.

[jawn101]

Ladies and Gentlemen (who am I kidding) - I am pleased to report that my spewing pump/power loss issue is 100% resolved!!

Before I continue any further it is very important for my own conscience that I start this post by saying that DMCH's new pump was **100% NOT AT FAULT** for the issue, and in fact was working as intended. It may even have saved me from a much bigger headache by doing what it was. I remain confident in the design of this part and very pleased overall with its performance.

That said, let's get on with the diagnosis.

After dozens of emails and a few hours of video chat with the incomparable Dave Swingle over the last few days, the culprit turned out to be none other than...

http://dmctalk.org/attachment.php?attachmentid=25005&d=1391306960

http://dmctalk.org/attachment.php?attachmentid=25006&d=1391306967

The high-pressure accumulator hose! As you can see in those photos (crap quality, but we all know that compartment is no easy place to see or photograph) the OEM hose had thermoformed a very hard kink in it. The pressure from the fuel pump must have been inflating it just enough for some gas to flow, enough to run the engine - but it was certainly a major restriction in the system. The weird thing was that the fuel pressure (tested with a K-Jet kit on loan) was 100% dead on at the fuel distributor. But that was at idle, with no way to test it under load.

http://dmctalk.org/attachment.php?attachmentid=25007&d=1391306973

Here you can see the hose cut out of the car and the extent of the kink. Everyone who is reading this post should please take this warning quite seriously - the OEM fuel lines on your car are *NOT* suitable for active use anymore! If you haven't replaced them all you are just asking for trouble. I have upgraded every one *except* these two at the accumulator, due to the difficulty of it. Look what that got me. The hilarious thing was that I had purchased new lines for this job and just had them waiting on my shelf. Very convenient that the fix ended up being a net $0 in parts!

Anyway, here's the beautiful result of all that work...


https://www.youtube.com/watch?v=fm95eIWHdEg

As you can see the pump runs smoothly and quietly, with no spewing. The baffle quietly fills up and overflows, just like it's supposed to. The sputtering under load with low fuel is gone.

Huge thanks to David Proehl, Clint W, Ryan S and especially Dave at DMCMW. Have you ordered anything from them lately?

[DMCMW Dave]

You have inadvertently settled another argument from long ago. The baffle will be full to the top all the time until the tank is dry.

This was interesting. . . .

A bit more detail - with the fuel link kinked, the "excess" fuel blew out through a relieve valve at the top of the pump. The fuel that got through the kink was enough to run the engine, usually quite well. The relieve valve excess came out with such force that it didn't land back in the baffle. There wasn't the usual return flow from the engine to refill the baffle due to the kink as well. The relieve valve is there to protect the pump in the event of, well, a kinked line or plugged filter.

Therefore the baffle ran low when the tank was low, effectively creating a hole in the pool of gasoline.

I contend that he would have noticed that the car ran out of power (gasoline) at wide open throttle very hard acceleration near redline, but he doesn't drive the car that way.

BTW - for future reference - a close to plugged fuel filter will cause exactly the same problem.

PS we also has some fun comparing the view out the front door.

[jawn101]

You have inadvertently settled another argument from long ago. The baffle will be full to the top all the time until the tank is dry.

This was interesting. . . .

A bit more detail - with the fuel link kinked, the "excess" fuel blew out through a relieve valve at the top of the pump. The fuel that got through the kink was enough to run the engine, usually quite well. The relieve valve excess came out with such force that it didn't land back in the baffle. There wasn't the usual return flow from the engine to refill the baffle due to the kink as well. The relieve valve is there to protect the pump in the event of, well, a kinked line or plugged filter.

Therefore the baffle ran low when the tank was low, effectively creating a hole in the pool of gasoline.

I contend that he would have noticed that the car ran out of power (gasoline) at wide open throttle very hard acceleration near redline, but he doesn't drive the car that way.

BTW - for future reference - a close to plugged fuel filter will cause exactly the same problem.

PS we also has some fun comparing the view out the front door.

Great additions, I should have included more of that. My mind is sort of soft from all the fumes today. Tomorrow I am going to verify that my mixture is still correct (this repair may have enriched it a bit) and then hit the highway with some gusto. See how she does. I have since filled the tank back up (took 13.2 gallons, so that should show just how empty I ran it) and it is driving great!!

Yes... we have very different views from our garages right now. You can have some of our perpetual spring if we can have some of your water....

[DMCMW Dave]

. You can have some of our perpetual spring if we can have some of your water....

Heh - our "water" is piled up 6 feet deep at the end of the parking lot now. Too dark for photos tonight.

[Tillsy]

Here you can see the hose cut out of the car and the extent of the kink. Everyone who is reading this post should please take this warning quite seriously - the OEM fuel lines on your car are *NOT* suitable for active use anymore! If you haven't replaced them all you are just asking for trouble.

Absolutely agreed - one part of my initial restoration before starting her the first time was replacing every fuel hose, and sure enough a number of them had splits and deformations. Only two I hadn't done were the FV lines as unfortunately it's not well known that most vendors have new stainless braided ones, so I waited on a specific particularly slow vendor. Now done and sleep much better knowing the last are replaced.

Fantastic to know the new pump was not at fault.

[NightFlyer]

WOW - What a completely unexpected end to that mystery. Glad it was finally solved and that the fix was cheap :thumbup:

With that said, the kinked hose that you removed looks different than the stock/OEM hose that was used at the accumulator, thus I'm wondering if that hose wasn't in fact a prior replacement somewhere along the line.

Anyway, thanks for following up and keeping us in the loop!

[jawn101]

WOW - What a completely unexpected end to that mystery. Glad it was finally solved and that the fix was cheap :thumbup:

With that said, the kinked hose that you removed looks different than the stock/OEM hose that was used at the accumulator, thus I'm wondering if that hose wasn't in fact a prior replacement somewhere along the line.

Anyway, thanks for following up and keeping us in the loop!

You're right, I have documentation that the line was replaced in 2010 (before I got the car) along with the accumulator. Just hard for me (and Dave) to believe anyone would use this inferior style hose that late in the game. But hey, anything is possible right?

[Bitsyncmaster]

I thought it funny that "OEM" hose still had the black cover on it. I never replaced my hose at the accumulator and that black cover completely fell off in pieces. I was getting worried I would need to do the hoses until I saw your last post that it was not OEM.

Nice to know the new pump has an overpressure relieve. Maybe that is the culprit rest pressure problem which is solved by an external check valve.

[jawn101]

I thought it funny that "OEM" hose still had the black cover on it. I never replaced my hose at the accumulator and that black cover completely fell off in pieces. I was getting worried I would need to do the hoses until I saw your last post that it was not OEM.

Nice to know the new pump has an overpressure relieve. Maybe that is the culprit rest pressure problem which is solved by an external check valve.

That kinked hose may not have been stock to the car, but it was definitely in the OEM style - rubber outer, braided intermediate layer and a plastic core. I think the problem I saw could definitely happen to the OEM ones as well, since I believe the plastic core to be the problem - it held the kink.

I wonder if you're right about that relief valve being partially to blame for the rest pressure issue. If true, I'm still glad it's there and think it was a very logical step for DMCH to add the inline check valve as part of the kit. That way you get the benefits of both for all of 5 minutes extra work.

Since it's still early here and the roads are unpopulated, I just hit a big, wide and empty 70MPH highway near my house for 20 miles or so of spirited cruising. There is a noticeable improvement in throttle response and acceleration at highway speeds now. I also noticed a much reduced if not totally eliminated effect of "bogging down" when running in a slightly higher gear at a lower speed. Example - I like to take the turn into my neighborhood in 2nd, and if I slowed down a little too much before turning in, I'd have some chugging while the motor caught back up. Don't have that now.

[NightFlyer]

The stock/OEM hoses are technically a nylon core. And although similar in appearance and design to the aftermarket kinked hose that you removed, they're also very different in terms of thickness of each layer - for example, the stock/OEM hoses have an extremely thin outer composite covering that frequently flakes off the braided fabric mid-layer, whereas the hose in your picture appears to have quite a thick layer of rubber composing the outer cover. Also interesting how the aftermarket hose in your picture doesn't appear to contain any markings on the outer cover, which IMHO screams cheap generic. While it's probably a good idea to change out the original hoses from the accumulator if one is still running them, I wouldn't necessarily call it an absolute necessity.

[jawn101]

The stock/OEM hoses are technically a nylon core. And although similar in appearance and design to the aftermarket kinked hose that you removed, they're also very different in terms of thickness of each layer - for example, the stock/OEM hoses have an extremely thin outer composite covering that frequently flakes off the braided fabric mid-layer, whereas the hose in your picture appears to have quite a thick layer of rubber composing the outer cover. Also interesting how the aftermarket hose in your picture doesn't appear to contain any markings on the outer cover, which IMHO screams cheap generic. While it's probably a good idea to change out the original hoses from the accumulator if one is still running them, I wouldn't necessarily call it an absolute necessity.

Fair enough. Though this hose did have printing on the other side and was originally sold to the PO by DMCCA.

[DMC5180]

One more thing about the OEM hose. Yes the OUTER sheathing cracks and falls off, but that does not mean the inner NYLON core is compromised (CRACKED,KINKED or LEAKING) It just looks BAD. I would like to know who the Original manufacture of that hose is and if they ever did any kind of long term testing.

I think it has been proven that NYLON core is better than TEFLON. Now I'm wondering what the the inner core is of the SS braided fuel lines is.

[NightFlyer]

One more thing about the OEM hose. Yes the OUTER sheathing cracks and falls off, but that does not mean the inner NYLON core is compromised (CRACKED,KINKED or LEAKING) It just looks BAD. I would like to know who the Original manufacture of that hose is and if they ever did any kind of long term testing.

I think it has been proven that NYLON core is better than TEFLON. Now I'm wondering what the the inner core is of the SS braided fuel lines is.

I concur about nylon being preferred to teflon. Most OEMs use nylon cored hoses.

I actually started a thread over on Today discussing the true value of the braided ss fuel lines that the various vendors offer:

http://www.dmctoday.com/showthread.php?472-Braided-Stainless-Fuel-Hoses-True-Benefit-or-Snake-Oil

According to Hervey's website, his are:

"Hand made Stainless Steel fuel lines using Teflon hose."

I posted a question inquiring what the core of DPI's braided stainless fuel lines are composed of, but Josh never responded:

http://dmctalk.org/showthread.php?8220-Delorean-Performance-Fuel-line-kit-Stainless-%28base%29&p=131400#post131400

Not sure what DMCH's braided stainless fuel lines are composed of - perhaps Dave S could answer this question :smile:

[kings1527]

Interesting coincidence. I'm going to be replacing my fuel accumulator when my new one arrives and I'm debating whether or not to replace that same line. Mine looks to be original to my car and I'd be replacing it with the same type of line that you did, Jon. I saw on the other thread how you had it ready to go in 15 minutes. Sounds like a pretty easy deal to make that connection to the hardline up in the car?

To my knowledge, the replacement line is flexible whereas the OEM is on the more rigid side. A part of me wants to keep that OEM hose in there and reduce the chance of the same kink developing that you had. Thoughts?

[jawn101]

Personally my opinion is to replace it. The kinked hose was not the new rubber-only style that is currently available. The kinked one was not OEM but was OEM-style at least. But my experiences are not indicative of what anyone else should expect. I am just a big fan of not taking any risks with gasoline.

[NightFlyer]

If the black composite outer sheath is sticky to the touch and flaking off, exposing the braided fabric mid-layer, then it's a stock/OEM hose. If not, then it's probably some kind of aftermarket replacement hose.

If the hose is stock/OEM and hasn't been stressed at all, then it should be fine. If it has been through a couple accumulator changes already though, then it's probably a good idea to change it out with a new piece of Gates fuel injection (high pressure) hose.

[Some guy]

So i got a phone call back in January telling me that they had like 100% failure rate with the check valve and they were thinking about a recall. They asked if i had problems with the check valve and i told them about the emails i sent them and how they told me i was the only person who had this problem and how my unit was out of warranty by a few months. "there was nothing they can do" I was one of the first people to get the "improved" unit. Now i can't get them to call me back about the recall.

At the end of the day i have just been buying from some were else. It is all you can do when company's do shady business.

I wish i stuck with the original, it worked for 30 years, this new one i have no faith in. DMC Huston dose not stand behind there product in my experience.

[Some guy]

After a day to cool off, i was harsh on DMCH. They are not shady. I think they got overwhelmed by this problem. (I know i did)

I was just heated up when i think about all the days and money spent trying to track down the check valve problem.

I would still order from them. I was assured by other dealers the only problem with the new pumps was the check valve.