Fuel system problem, i am out of ideas.

[Some guy]

Hi so i have made a few posts about my K jet system and each time i think i finally figured it out. It still dose not work.

The problem i am having is the my system will not hold pressure more then 10 minutes. (I timed it) once it looses pressure air gets in the lines and it will run like crap till the air gets out of the line. Then it idles perfectly at 750 RPMs. If it has been sitting over night it will take as much as a 2 miles for the system to be back to normal running.

I have replaced the Accumulator, fuel pump, rubber o-rings in the distributor pressure valve, fuel filter, and 2 bad injectors. The other 4 injectors seamed to work identical to the 2 new ones in "spray" and "hold pressure".

I have the Cold start valve jumper-ed so that it fires as i am cranking the engine. (This is so that it starts every-time)

I cleaned the warm up regulator. I took it apart and cleaned metal plate valve-ish thing there.

I did all of this and it runs great when it is running. It is smooth and sounds great.

Here is my list of ideas;
1 the rubber o-rings in the distributor pressure valve are bad, or wrong size (I got these o-rings from a DMC dealer)
2 distributor has leak (from where i have no idea)
3 fuel system is cursed.

I am going to give it one more shot and then take it to DMCca and have them take a look at it.

[Jonathan]

Your list looks to have covered most of the main culprits.

Without any smoking gun to point out to you, perhaps just go back and double check the connections are all as they should be? Electrical, vacuum hoses, fuel lines, spark plug wires, etc. I'm definitely not trying to underestimate your abilities at all, but it might have been a simple enough problem, that you didn't see it and went straight for the bigger possible issues. Make sure all plugs and screws and what not are in place and accounted for, microswitches are calibrated, etc.

If you need any help with diagrams on routing, or connections, or wiring or whatever, just ask. Most of it is readily available in the resources section or elsewhere.

[DMCMW Dave]

Re-check the rings in the fuel distributor. These never go bad, unless you change them. Then they seem to tear from time to time. Especially the small one.

[David T]

To hold rest pressure you can have no external leaks, the fuel pump check valve has to hold and the Primary Pressure Regulator can't leak. And the accumulator can't have a bad diaphragm. That's it. Hard to actually see and test the PPR and the fuel pump check valve, you just replace the "O" rings in the PPR and the check valve at the fuel pump. It is VERY important that you get the correct "O" rings and assemble the PPR without damaging them.
David Teitelbaum

[Bitsyncmaster]

You would need to disconnect some fuel lines and narrow down the problem like that. I would start at the line supplying fuel to the FD. I have seen some bad accumulators that were new from some vendors. It does not take much volum of fuel leak to drop the hold pressure.

[Some guy]

I will check the o rings on the pressure regulator tonight.

Is there any real chance of the frequency valve having a leak and that being the culprit?

I like the idea of testing the lines. What do you think of disconnecting the fuel return line and starting from there. If my frequency valve or O-ring is leaking, that should show up there?

I did put a second fuel check valve in line, because i though the one on my fuel pump could be bad.

[Bitsyncmaster]

If you had some old fuel hoses, you could make up a plugged line (pressure gauge in the end) and then find what is leaking.

Your leak is pretty bad. You could pull the vent line off the accumulator and see if it leaks there.

[Some guy]

I have pulled the line off the accumulator. It only leaks out what was in the hose.

I have seen a lot on here about a fuel pressure gauge. Do you have one you recommend?

[Bitsyncmaster]

I have pulled the line off the accumulator. It only leaks out what was in the hose.

I have seen a lot on here about a fuel pressure gauge. Do you have one you recommend?

I built my own with some old fuel hoses. Any 100 PSI gauge will work if you do that. I think you can buy a unit for our engine for less than $100.

[DeLorean03]

I have pulled the line off the accumulator. It only leaks out what was in the hose.

I have seen a lot on here about a fuel pressure gauge. Do you have one you recommend?

Right here, sir:

http://www.thetoolwarehouse.net/p-6972-tool-aid-33865.aspx

[Some guy]

So this is just baffling me. I pulled the return tube off the fuel distributor. brought it up to pressure (the plate was hard to move) and not a drop leaked out of the return tube hole. i had a flash light looking, waiting for a drop to come out and nothing.

I am going to look at my accumulator return tube again. I will pull it off, plug it and jumper the fuel pump(so that it is running) and see if any gas leaks out.

i am just tired of fighting this. I have so many other things on the car that need to be fixed.

I just have to pay and have someone look at this i think.

[Bitsyncmaster]

So this is just baffling me. I pulled the return tube off the fuel distributor. brought it up to pressure (the plate was hard to move) and not a drop leaked out of the return tube hole. i had a flash light looking, waiting for a drop to come out and nothing.

I am going to look at my accumulator return tube again. I will pull it off, plug it and jumper the fuel pump(so that it is running) and see if any gas leaks out.

i am just tired of fighting this. I have so many other things on the car that need to be fixed.

I just have to pay and have someone look at this i think.

Good work. That tells you the PPR o-ring is sealing and the FV is not leaking.

[Some guy]

So after all my work trying to get the fuel system to hold pressure, it ended up being not 1 but 2 bad check valves. The one on my "New and improved" fuel pump and an after market one i bought on amazon.

I am so mad. i can't get a break on this car. I email company XXX 3 times about the check valve and they will not even email me back. I spend thousands with them and not a word about a flap of rubber.

Hundreds of dollars spent trying to fix a hot start issue and it was a defective part from the beginning!!!!

Hours and hours of work for nothing!!!!!!!

[DeLorean03]

So after all my work trying to get the fuel system to hold pressure, it ended up being not 1 but 2 bad check valves. The one on my "New and improved" fuel pump and an after market one i bought on amazon.

I am so mad. i can't get a break on this car. I email company XXX 3 times about the check valve and they will not even email me back. I spend thousands with them and not a word about a flap of rubber.

Hundreds of dollars spent trying to fix a hot start issue and it was a defective part from the beginning!!!!

Hours and hours of work for nothing!!!!!!!

Would you be willing to disclose who this was? Especially after the "new and improved" part, I am sure a lot of us are curious.

As for the DeLorean, remember, it's not the car's fault. This is just the way it is with working on 30+ year old cars. Not trying to say "tough - deal with it" -, I am just saying "It's worth it."

[David T]

This is just another case of where, if you patronized one of the Delorean venders, you would have gotten a part that worked in the first place, and if you had a problem they would have stood behind it and replaced it. Any savings you might have had are now long forgotten. It is also another example of where you must suspect even new parts when you have a problem. Just because it is new, you cannot assume it must be good. As you have now learned there are only 4 ways you can lose Rest Pressure:
1) A bad fuel accumulator
2) A leaky check valve on the fuel pump
3) A leaky Primary Pressure Regulator
4) An external fuel leak
Listed in order of likelihood.
David Teitelbaum

[Some guy]

I don't want to bad mouth a vendor. They were great to me other then this. (it was a Delorean vendor, and they are not standing behind it. They will not email me back)

You are right about the loss of rest pressure, i replaced all those parts, when i didn't need to. (wasted time and money)

The problem is when i got my car nothing worked, i had to fix everything and i had no way of knowing the check valve failed under pressure. If i blew into it, it worked fine.

The reason i am mad is because i had to read on here that the check valve was known bad on this unit. I spent months trouble shooting, trying to figure out why the car would not hold pressure. Ordering even more parts from this vendor.

The icing on the cake was the second bad check valve i order on amazon. the dam thing had a slice right through the center of the rubber flap.

[Ron]

As you have now learned there are only 4 ways you can lose Rest Pressure:
1) A bad fuel accumulator
2) A leaky check valve on the fuel pump
3) A leaky Primary Pressure Regulator
4) An external fuel leak
Listed in order of likelihood.
David Teitelbaum
You may want to insert the injectors (including Cold Start) in the list.

[DeLorean03]

The problem is when i got my car nothing worked, i had to fix everything ...

One of these days, I'll tell you my story. I completely and totally in every single way know and understand how you feel there - believe me.

[David T]

I have yet to see a cold start valve leak. I suppose there are ways you could have leaks internally where you wouldn't easily notice besides the obvious external ones. I would guess over 95% of the hot restart problems are due to A) a bad accumulator, B) a bad check valve, or C) a leaky PPR with C being a possibility only if it was ever messed with.
David Teitelbaum

[Jonathan]

One of these days, I'll tell you my story. I completely and totally in every single way know and understand how you feel there - believe me.

Yep. Let me know if you think you might write it all up one day as I think I could help write a few of the chapters for this book as well ;) Not everything on my car wasn't working when I got it, but it was close...

[Ron]

I suppose there are ways you could have leaks internally where you wouldn't easily notice besides the obvious external ones.Sure...the 6 injectors are under rest pressure (~43psi. ~8psi away from opening pressure). I'd guess it's not too uncommon after seeing 2 SEDOC members having "hot start" problems (flooding) after installing some reconditioned ones that leaked.....
Something else to look for anyway.

[David T]

You're right. If the control plunger is leaky AND you have leaky injectors that can also cause you to lose Rest Pressure prematurely. In fact that is probably what eventually drops the Rest Pressure anyway. I still maintain the biggest culprits are the accumulator and the check valve. Refer to D:01:14 for a full explanation of the Rest Pressure circuit.
David Teitelbaum

[Ron]

As seen in D:01:14, the upper chambers and lines going to the injectors are both part of the rest pressure circuit, with the plunger separating them from the remainder (when closed). Since both sections are under pressure when the engine is shut off, the plunger DOES NOT have to be leaky for a bad injector to dump fuel, flood the engine, or cause a loss of rest pressure. (Note 6 lines and 6 chambers full of fuel, under 3bar pressure...after everything else settles down.)

I'm sure you have seen/know what happens if you loosen an injector line at the FD after a shut down...or bumping the pump...