3.0 hot start problem

[lazyeyedog]

Hi, I'm new to this message board, so forgive me if this question has been asked before. I recently purchased a 79' 911 SC Targa ( the car I always wanted since I was about 3!) It's a great car, but it has this problem-

On a cold start (sitting overnight) it fires up like a champ.
If I stop to run into a convienience store, or to get gas, it fires right back up.
It's when it sits for about an hour after fully warming up that it doesn't want to start back up.
It WILL always start, but only after exessive cranking, and when it does decide to start, it runs rough at a low rpm for a couple minutes.
Is there an adjustment for the cold start injector or something?
This condition is especially embarrassing on a date as you can imagine!

Also, I was wondering what oil pressure is acceptable at idle with a fully warmed up engine.

Thanks for your responses

[MBEngineering]

HI lazyeyedog
you will need to get checked out the fuel system , I would prob say the fuel return valve in the fuel pump is not holding pressure when hot, I have photo'd the K-jet test info for you below;






sorry the lines do not line up correctly for the info path from one sheet to the other.

If you follow the plan through and work out which way your car is faulty you should be back on the road in no time. the fuel pump is under the front of the car at the back of the fuel/gas tank, take care when working on the fuel system with heat and open/live wires.

regards mike

[wilke3169]

My '79 had these same symptoms. I replaced the fuel accumulator. Located near the fuel filter in the engine compartment. No real way to check it as far as i know but it cured my problem.
It's found on this page of our hosts offerings...

http://www.pelicanparts.com/cgi-bin/ksearch/pel_search.cgi?please_wait=N&forumid=&threadid=&command=DWsearch&description=accumulator&FILTER_911M=ON&FILTER_TECH=ON&FILTER_SUPP=ON&FILTER_ACCE=ON&FILTER_CARE=ON&FILTER_STUF=ON&FILTER_PERF=ON&FILTER_MISC=ON&FILTER_GADG=ON&FILTER_TOOL=ON

[cmonref]

Those CIS test procedures are for CIS systems before the accumulator grew a return line to the fuel tank. LazyEyeDog's '79SC has the three-line accumulator.

LazyEyeDog: The leak may also be thru the accumulator -- it is a fourth "possible cause" as listed on the right side near the top of the second page. To test this, loosen the lower fuel line connection on the accumulator -- leakage of fuel means that the diaphram inside the accumulator has ruptured and the accumulator will not hold residual pressure after engine shutdown. The accumulator must be replaced. I would do this test before the other tests listed in the procedures above after "possible causes."

[johndglynn]

The fuel pump check valve is cheap and a no-brainer to change, I would replace that first and see what happens. The accumulator would be my next port of call.

Welcome to the board

[ramonesfreak]

ive been having the same problem. i recently ordered a fuel accumulator and check valve. i should have them installed by saturday and will repost if they fixed my problem

when i removed my accumulator, fuel leaked out the bottom when i removed the line coming off the bottom. i recall seeing a thread on this board saying that if fuel comes out the bottom, its a sign that it has failed

in general, a hot start is usually the accumulator or check valve

these are the parts needed for the 3.0...though note that if your fuel pump is pre-1980 it may have an internal check valve

893-906-093-M5014
Check Valve, M12 X 1.5 - M12 X 1.5 911 1980-83
Brand: Bosch - Por
$25.00


911-110-197-02-M14
Fuel Accumulator, 911 Turbo 1978-94Each
Brand: Bosch
$242.50

[cmonref]

Check the accumulator first -- not the fuel pump check valve. It is a 5-minute check, costs nothing, and is the highly probable cause of your problem.

There is no independent test for the check valve -- you buy one and install it. After you have jacked up the front and removed the suspension plate and managed to leak fuel onto yourself and the floor. Again, test the accumulator first.

[ramonesfreak]

Brian, its too late for me as I have removed the old and ordered a new one, but how does one "check" the fuel accumulator?

[cmonref]

scoTT: Right -- I was commenting on John's advice to LazyEyeDog.

By the way, wouldn't a '79 SC use the -01 version of the accumulator for $134.25?

[ramonesfreak]

gotcha. can anyone confirm that if fuel pours out the bottom of the accumulator that its bad? that seems to me to be the only way to check it. mine poured out as soon as i removed the line which would indicate its not doing its job? i could be wrong

[cmonref]

Yes, if fuel comes out the bottom of the accumulator, it has failed. There is a diaphram that separates the fuel chamber from the bottom connection on the accumulator -- that bottom part of the accumulator is dry until the diaphram develops a hole.

[johndglynn]

I personally would always change both in sequence: check valve/accumulator. Then you know you are done with tank to motor pressure worries for another 20 years. Easy enough to do the front end job without peeing fuel all over yourself, done it a few times on various 911s.

If you get into the front end work, buy some new cotton reel mounts for the fuel pump before you drop anything. They're a good 'while you're in there'. You'll find out all about those jobs as you spend more time here

[ramonesfreak]

fuel accumulator

[Wayne 962]

A bad fuel accumulator or a bad fuel pump check valve will cause hot start problems like this. It's usually one or the other...

-Wayne

[ramonesfreak]

I ordered these parts from you Wayne the other day, got them just a few days later, and installed the FA today. Thanks !!

due to intense rain, i have not had a chance to test my new part(s) though. Your 101 book and this forum lead me to the conclusion that these parts are suspect, so, thanks again

Though I cursed a few times installing them...in my mind i was thinking about your book which says "one of the easiest jobs to do....." hahahah. man i had a tough time.

[boyt911sc]

Originally Posted by Brian K. Haggard

Yes, if fuel comes out the bottom of the accumulator, it has failed. There is a diaphram that separates the fuel chamber from the bottom connection on the accumulator -- that bottom part of the accumulator is dry until the diaphram develops a hole.

TO : Brian and others,

The lower section of a three-port fuel acumulator contains fuel all the time when the fuel pump starts to run. This is another MYTH that has propagated and misunderstood for quite sometime. The bottom port is a drain line in case the FA leaks. Even for good FA, the lower section of the accumulator has fuel in it because it is connected to the main fuel return line going to the fuel tank. Thus at anytime during operation, circulating or returning excess fuel from the fuel distributor is returned to the tank.

So fuel coming off from the bottom of the FA is not a good indicator that the FUEL ACCUMULATOR is defective or the diaphragm has ruptured. It might be fuel from the return line. But a ruptured diaphragm will leak at the bottom. One simple way to test a FA is to pressurize it. Sometimes you could tell it by blowing air using your mouth if the rupture is big enough but pin holes is not easily detected by this test.

I'm hoping that people will remember that there is always fuel present in the lower chamber of a three-port FA (good or bad). HTH.

Tony

[MBEngineering]

+++ for tony(boyt911sc)
You beet me to it , If you have a non fuel return pipe in the bottom of the FUEL ACCUMULATOR, then remove the small screw and see if fuel comes out , and yes it is leaking and needs replacing, the only way to check if the FUEL ACCUMULATOR with the fuel return line in the bottom, is with the pressure gauge and clamp off the feed pipe at the tank, that is if you want to check or just change things and not to bother to check through a usable test plan , even if it is for a older car, It will give you the basic direction to go in to check thing out, but then a gain who am I to let you know what to do or not to do!! it's your $$

regards mike

[eubanksae]

Hey guys,

I've got the same warm start issue, and I've already replaced the fuel accumulator. I'm not seeing the check valve listed on Pelican for my vehicle (1978 911SC). Can anyone direct me to the part?

[ramonesfreak]

eubanksae, i could be wrong but i think your stuck buying a new fuel pump. i think that pre-1980 cars have the check valve inside the fuel pump and thus, not serviceable

maybe others can elaborate

[eubanksae]

Scott,
If it's truely not replaceable, would the following work?

So, the problem it's causing doesn't appear to be restrictive, but rather, it's letting fuel pressure bleed down. Could I not just add an external check valve just above the pump? In my infinite ignorance; I'm basing this theory purely on pictures, I haven't actually looked at my fuel pump yet, to guess at how I might accomplish this.