CIS hard to start when hot

[1fastredsc]

I know this subject has been beaten, but. Usually the cause of hard starting when the engine is hot is because of the fuel accumulator. Well i replaced mine, and for some reason, the hot starts are still a little rough. It seems like it'll start by running on 2-3 cylinders, then as the fuel lines pressurize it slowly works it's way to running on all 6. Is there typically other things i can look at that possibly are the cause for the fuel lines to lose pressure when sitting hot?
Edit: Also, it will not start at all if i let the motor sit hot for about 30 minutes or more. Then i have to go to the motor and push on the fuel meter plate by hand to manually give it a shot of fuel.

[MotoSook]

How do you know the fuel line pressure is increasing?

How long does it take for the rough running to go away?

Did you run a residual pressure test on the system? A bad check valve won't hold line pressure even with a new accumulator.

[1fastredsc]

I'm not positive on the fuel line pressure increasing/decreasing. This is my assumption based on the odd charateristics of the problem. For instance, when hot, if i shut it off, wait say 30sec or so then fire it back up, no problems, everything runs fine and starts with less then a full crank. But the longer i let it sit hot before 30min (roughly), the fewer cylinders it will run on when i start it back up, after 30 min it won't fire at all. The reason i assumed it is loss of fuel pressure is because i assumed that based on the different lengths of fuel lines, the longer ones will take longer to pressurize than the short ones. Which in my head explained why the longer it sits hot the fewer the cylinders will fire. Of course i could be very wrong about this which is why i posted this thread.
EDIT: Oh and it takes usually about 10 sec of idling with the help of the throttle to get all six going.

[CARRERIC]

Look for rust in your tank. If rust has entered the cis system you will have these symptoms. Take out your fuel filter and blow gas aout backwards int a jar and check for rust particles.

[dmarv]

I had the same problem on my '76. Changed the warm up regulator and problem solved.

[konish]

I'm with Souk on this one. Did you check you fuel pump check valve?

r/
Dustin

[1fastredsc]

No i haven't, that's probably a cheap enough check up.

[sammyg2]

If it is caused by vapor lock in the injector lines (and it sounds like it is) that is caused by the pressure in the lines dropping faster than they can cool down which causes the fuel in the lines to boil.
A bad accumulator will do this, a bad check valve will also do this, as will leaking injectors.
It is relatively easy and cheap to replace a fuel pump check valve.
It is also faily straightforward to pull the injectors and put them in jars to watch for leakage.
I'm betting one of these things will solve the problem.

[Gunter]

Check valve before anything else. If there are a lot of miles on the pump maybe now is the time for a new one. And a new short piece of 1/2" (12mm?) hose. Since you disconnect for a new check valve anyway, drain the tank and take a look at the screen/filter in the center of the tank. (Large hex plug)

['78 SC]

While we're on the topic, John Walker posted some part numbers here for the fuel pump check valve (1 583 386 514) and the one that mounts on the fuel distributor inlet (1 587 010 004). Neither of these gives a hit on the Pelican parts search. What am I missing?

[1fastredsc]

Originally posted by sammyg2
If it is caused by vapor lock in the injector lines (and it sounds like it is) that is caused by the pressure in the lines dropping faster than they can cool down which causes the fuel in the lines to boil.
A bad accumulator will do this, a bad check valve will also do this, as will leaking injectors.
It is relatively easy and cheap to replace a fuel pump check valve.
It is also faily straightforward to pull the injectors and put them in jars to watch for leakage.
I'm betting one of these things will solve the problem.

That's actually what made sense in my head, although i thought the accumalator or fuel injectors were possible causes (both of which are new). Didn't think about the check valve, i'll get on replacing that soon so that i can report back. Thank you.

[1fastredsc]

I pulled the check valve out today. Tried putting air pressure against the opposite direction of flow to see if it would leak and it doesn't. Is there another way to test it or is it good?

[vash]

i may be incorrect, but i think the most surefire way of finding it is to use a CIS pressure tester gauge. run the car with the gauge hooked up, and shut it off. i think you want to see better than 16psi after 30 minutes. at least that tells you If there is a problem.

[wicks]

Which was it? Warm up reg, check valve?

[kavadarci]

This sounds like my problem.
Subscribed but my plan is to replace the accumulator it’s old with the car, fuel check valve and r pump which is really noisy.

[Bob Kontak]

Originally Posted by wicks

Which was it? Warm up reg, check valve?

Bummer is this thread is 13 years old.

Problem seems to still be around though.

[proporsche]

hi Bob you are funny..the problem was there in the 1980`s;-) already...

Ivan

[theiceman]

sucks when guys come looking for help though, get lots of it, but never come back and update us on the fix.

[proporsche]

Hi iceman..could be economic problem...maybe they have sold their 911..?

ivan

[rwest]

Originally Posted by theiceman

sucks when guys come looking for help though, get lots of it, but never come back and update us on the fix.

OP was on here last in 2011.

I “joke” that when someone asks troubleshooting questions on a forum, they should have to put down a deposit and they get it back only if they follow up with what fixed the problem.