xBLACKx

Car: 1988 Audi 90 Quattro
Engine: Inline 5 with CIS mechanical fuel injection (10v NG)

I have been battling a starting problem since I have owned the car. If the car has been sitting for over an hour, the car will turn over, fire, then die immediately. (The cold start valve is working.) To start the car, I have to push the gas pedal and crank for two seconds untill the car will start to turn over, the engine will stumble for about 2 seconds, and then idle perfectly. This does not happen if I shut the car off, and then return to the car within 30 minutes , as it will fire and run like a new car.

I have replaced the fuel distributor and fuel pressure regulator with known working units. The fuel filter has also been replaced with a new bosch unit. I'm leaning towards thinking the problem is the check valve or the fuel accumulator. Fuel pump would just stop working if it were bad. I have also checked for vac leaks which I have found none.

Through searching and reading, I have come to these possible conclusions:

1) Fuel pump is going out
2) Fuel Accumulator needs to be bypassed.
3) Fuel Check valve needs to be replaced
4) Injectors need to be cleaned.

Anyone have any insights into my problem? Im going to start tackling this problem this weekend.

Loudgoldwing

Easiest way to find out is:

For your first attempt at a cold start, turn your key all the way to JUST BEFORE the "springy" point where you starter turns. LEAVE IT THERE for 20 seconds in order to give the fuel pump an opportunity to push fuel all the way up to your injectors. Sing softly to yourself, recite **** or poetry, whatever... after a full 20 seconds of your warning lights flashing at you... THEN turn your starter over.

If the vehicle fires up right away, it's a fuel pressure issue. Read on... if it doesn't, skip the next bit and go directly down to the "NOT FUEL RELATED" paragraph below.

The most likely culprit of a fuel related issue (given your description at least) is the check valve. I only say this because you haven't complained about the running of the vehicle on the freeway, i.e. higher RPM's. If it were running crappily at high RPM's that would be a sign of a filter or pump issue. As it stands right now, you're only saying this is a start-up issue. The check valve snaps shut when you shut your engine down. This keeps fuel up at your injectors until you go to start up again, even if it's a few days. Most likely, you have a piece of grit in your check valve, and it's allowing the fuel to seep slowly away. The longer you let it sit, the worse the problem gets.


NOT FUEL RELATED: If the 20-second key trick doesn't work, I'd say you need to change your spark plugs and ignition wires, as what you've described is frequently a sign of humidity being allowed to condense in your plug wells. Before your next cold start attempt, spray some WD-40 down into your plug wells (LEAVE THE PLUGS AND WIRES AS THEY ARE) and let it sit for about 10 minutes. If the engine fires right up, you'll know that the WD-40 has chased away whatever condensation had built up, and your plugs are free to be hot and happy.

Good luck!