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

[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://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...

[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.