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

[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 !

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.

DSCF0173.jpg

DSCF0174.jpg

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.