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

[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:



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

[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:



It can be purchased for $38.05 shipped from here: http://www.ebay.com/itm/SUR-R-CKV5-5...207#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:



It can be purchased for $11.08 plus shipping from here: http://www.usplastic.com/catalog/ite...5394&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:



It can be purchased for $7.99 shipped from here: http://www.ebay.com/itm/5-16-8mm-One...fb0c51&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:



It can be purchased for $9.98 shipped from here: http://www.ebay.com/itm/5-16-8mm-Inl...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://valves.specialtymfg.com/produ...n-check-valve?

Again, it can be purchased for $11.08 plus shipping from here: http://www.usplastic.com/catalog/ite...5394&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

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.