streetsnake

So I just got done bragging about my new finished-up top-end refresh and I go out to take it for a long drive and it doesn't start. Ugh. (Cue pie in the face ) I know I need a new fuel accumulator, as during CIS testing it looked to be bad, so I figured that is what the problem was. That is my first question...can someone explain to me what the fuel accumulator does and why it is needed. (In dumbed-down terms) I know after the car has been running awhile and it won't start back up, that is the likely culprit but can't understand why it's there and what it does.

So onto the rest of the story. I let the '79 cool down for awhile (2+ hours) and go to restart and still no fire. I decide to bump the fuel pressure up a smidge and it fires up although not happily. It idles down and stalls. I start it back up and give it a couple of revs and all is right in the world, other than it still idles higher than I'd like and unfortunately, the idle screw does not fix it. So when I was testing this morning I leaned the mixture out and it ran great but then it wouldn't start when I went back. Could advanced timing be the culprit of this... not wanting to fire although when testing it liked the leaner mixture.

Hopefully my rambling is coherent enough to follow. Thanks

GerritD

Hi,
I have a likewise issue with my Euro CIS 928S of 1980.
Car starts fine when cold, or warm within the hour. But when it sad for more than 1 hour after running, I need to crank it 2x 5 seconds before it catches.
Fuel accumulator is only there for warm starts. When engine is warm and you stop the engine for some time, the fuel vaporates in the fuel lines, but the fuel accumulator
prevents this because it keeps the fuel lines pressurised for some time. ( some time = long enough so that fuel doesn’t vaporates anymore)
Ofcourse, difficult warm start can have 4 root causes :
- bad fuel accumulator ( leak at the membrane and so fuel leaks at the screw on the top)
- bad fuel pump check valve
- FD pressure relieve valve
- leaking injectors

At my CiS system, I have or a bad fuel pump check valve, or a leaking fuel accumulator since the FD pressure relieve valve keeps my rest pressure of 2,7 bar for 30 minutes
and my injectors are new since 1 year.

Petza914

Have you tried pushing the gas pedal all the way to the floor (not pumping it, just holding it wide open) when cranking it when hot. This often does the trick.

The other thing to check is whether the cold start injector is flooding it when it's not supposed to be firing because the temp sensor that controls that is bad. You can test this by disconnecting the electrical connector from the injector and see if it starts right when hot as that will keep it from adding fuel.

streetsnake

Thanks Pete. I’ll try holding to the floor when engine is warm and try to get a video posted to YouTube for a cold start-up

Dmhager

If your fuel pressure goes down fast after you turn the car off, warm starts will be a problem, even if you press the pedal to the floor - lots of cranking will be required and lots of turning of the key (the pump runs briefly if the engine doesnt fire IIR so just holding the accelerator on the floor while you crank doesnt bring up the fuel pressure). With CIS cars, the fuel system needs to be complete and setup properly (i.e., functioning accumulator, check valve at the pump, and pressure regulator in the FD, correct pressure settings at the FD and WUR, and fuel delivery rate - just the routine stuff as outlined in the WSM and/or on 928classics.com). The accumulator also provides damping for the fuel system while the car is running (you can feel the pulses by putting your fingers on the fuel lines upstream of the accumulator). The continuous injection system likes continuous pressure at the FD and the injectors. Through experience, the first thing I do with any CIS car I get is go through the entire fuel system from tank to injectors and make sure its all there and all working properly before I do anything else.

Rob Edwards

To paraphrase Jim Bailey, "Cold and warm control pressures, cold and warm control pressures, cold and warm control pressures." Everything else is just bandaiding symptoms.