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

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

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.

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Originally Posted by 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

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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

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

I just ordered my check valve. :)

George

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.

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Originally Posted by 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.

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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-Va...Rlg~~60_12.JPG

http://www.ebay.com/itm/5-16-Check-V...df8304&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-...Ghg~~60_12.JPG

http://www.ebay.com/itm/5-16-8mm-One...249e78&vxp=mtr

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.

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Originally Posted by 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.

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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.

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Originally Posted by DMC5180

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.

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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.

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Originally Posted by 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.

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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-Inli...JvQ~~60_35.JPG

http://www.ebay.com/itm/5-16-8mm-Inl...f5c52a&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...

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.

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.............

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Originally Posted by Jimmyvonviggle

Can someone explain to me what this thing does....

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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.

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Originally Posted by Rich

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.

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

Chuck

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Originally Posted by virtualchuck

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

Chuck

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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.

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.

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Originally Posted by 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.

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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.

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

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Originally Posted by Henrik

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

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

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Originally Posted by NightFlyer

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

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+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.

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Originally Posted by cybercusp

+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.

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

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?at...7&d=1378665167

http://dmctalk.org/attachment.php?at...8&d=1378665356

George

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

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Originally Posted by 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

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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.

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Originally Posted by 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

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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.

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Originally Posted by Delorean02378

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

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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.

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Originally Posted by StainlessBullet

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.

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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?

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Originally Posted by thirdmanj

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?

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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.

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Originally Posted by NightFlyer

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.

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

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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.

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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

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/o...ps49c25eae.jpg

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

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.

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Originally Posted by 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?

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

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-Va...Rlg~~60_12.JPG

I purchased it from here for $14 shipped: http://www.ebay.com/itm/5-16-Check-V...df8304&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/ima.../22398psku.jpg

I purchased it here for $11.08 plus shipping: http://www.usplastic.com/catalog/ite...5394&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.

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...

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Originally Posted by 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...

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

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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.

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It can be found here: http://dmctalk.org/showthread.php?79...l=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!

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Originally Posted by NightFlyer

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?79...l=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!

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

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.......

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Originally Posted by 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/o...ps49c25eae.jpg

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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