Uneven Injector Output ***Split from PPR Shim Source ***

[bytes311]

Sorry...I didn't mean to imply anything like that! -- It seemed like you were about to drop some bucks w/o trying the test(s)...

Yes and Yes! As I said before, the WUR dumps primary pressure to create control pressure. If it can't dump the fuel because of a blockage nothing changes and they will always match.

Restricting only when it goes over 65 is odd! So, since you also started seeing trash, I'd go back to cleaning it out from the fuel filter on then trying the test. If it passes, start from scratch with the gauges.

EDIT:
To be clear- I should have said, "Blocking" (total restriction), instead of, "Restricting only...."

Thanks Ron! I'll perform some more tests tonight.

[bytes311]

Silly question, but if I disconnect the return line between the WUR and the FD at the FD side and place the hose in a jerrycan and jumper the RPM relay, is that opened port on the FD going to spray fuel?

[Ron]

Absotively posilutely!

...
You must plug the port on the FD where it connects or fuel will escape from the FD!!!

[MikeWard]

Not that one. Tyhat one is one of the two that comes in the kit you linked to (#1 in the discussion post 52). It seems a third one marked with a "?" in post 52 and inside the section marked with an arrow in your pic below just isn't included in the kit. It's only job is to "fully seal off the control-pressure circuit with absolute certainty when the engine has been switched off " as in post 59, so it should be in the kit, imho.
Attachment 60005

EDIT:
Attachment 60006

Ah I see what you mean.

I'm sure if someone was to take the time to remove that part, take measurements of the i/d, o/d and thickness of the o-ring and then get in touch with Arran at DeLoreanGo to provide that info, he could look to add that o-ring into the kit.

[DeLoreanGo Arran]

That o-ring is already in the fuel distributor rebuild kit, but as far a "quick fix hot start" is concerned it is only ever the one on the very tip that is the problem as it is a moving part. The one on the outside of the shaft and the copper washer are also provided in the "quick kit" because they get disturbed when you replace that o-ring. The (third) internal one is something you'd only ever touch as part as a more in-depth rebuild, hence why it's in the full rebuild kit.

[Bitsyncmaster]

That o-ring is already in the fuel distributor rebuild kit, but as far a "quick fix hot start" is concerned it is only ever the one on the very tip that is the problem as it is a moving part. The one on the outside of the shaft and the copper washer are also provided in the "quick kit" because they get disturbed when you replace that o-ring. The (third) internal one is something you'd only ever touch as part as a more in-depth rebuild, hence why it's in the full rebuild kit.

I have had a few customers complaining of hard cold starts which they seem to find starting better with the CSV pulled. Hence their mixture seems to rich. One guy sent a video of his air plate which you could see bump up a little during his cold start. I wonder if that internal O-ring has anything to do with that cold start problems.

[bytes311]

Absotively posilutely!

Oops, I missed that. Thanks Ron.

So I took my WUR to that fuel injection shop and they bench-tested it on the spot. Pressures are good and within spec, which I believe now makes the FD the prime suspect.

[David T]

During a cold start the motor is starting on the fuel from the CSV til the pressure gets up high enough for the injectors to start spraying. Without the CSV you will be cranking the motor longer till the fuel pressure gets high enough for the injectors to spray It is possible to have the wrong plug on the CSV. The plugs might be swapped with the CPR. That would make the motor run VERY rich! I would have those customers double-check the plugs. Or there is a problem with the wiring in the cold start circuit or the Thermo-Time switch is defective and the CSV is running all the time. Ask them if there is anything plugged into the hot start relay plug. There are all kinds of possibilities. On one car that was hard starting I found the "O" ring missing where the cold start valve attaches to the pipe. Sometimes the bolt holding the pipe is loose or one of the seals is missing. Once in a while I find the brass ring that holds the "O" ring in the bottom of the mixture unit dangling on the idle motor pipe. It is a difficult place to inspect which makes it all the more important to see what's going on under there. The point here is if the motor is not starting right there is a problem and you have to keep searching till you find it. I don't like replacing parts till I get lucky. I like to figure out what is wrong and then replace only the defective part. We are assuming the hard cold start problem is caused by the fuel system. A problem with the ignition can also cause hard cold starts.

[Ron]

I have had a few customers complaining of hard cold starts which they seem to find starting better with the CSV pulled. Hence their mixture seems to rich. One guy sent a video of his air plate which you could see bump up a little during his cold start. I wonder if that internal O-ring has anything to do with that cold start problems.

I wouldn't think so. If residual pressure from the WUR's return line can't get past the PPR's piston, it can't go anywhere, i.e., cause a rich condition.

Removing it wouldn't cause it to fail the rest pressure test, just shorten the time... The early style (pre-D) PPRs/FDs didn't have one. And I assume they found that fuel would weep between the piston and bore (?after wearing a while?), allowing pressure in the WUR's return line to drop. Whatever the reason, it was added for better residual pressure.

[Ron]

Ah I see what you mean.

I'm sure if someone was to take the time to remove that part, take measurements of the i/d, o/d and thickness of the o-ring and then get in touch with Arran at DeLoreanGo to provide that info, he could look to add that o-ring into the kit.