924Board.org

[plyhammer]

I have a 79 na and it sometimes will not start back up after shutting off. Most of the time I have to wait an hour or so and then it starts again. I assume this is the hot start problem. Anyone know what part I am looking for to fix this problem myself? Thanks

[Smoothie]

The problem is vapor lock when you have the hot start problem and that's caused by pressure not being held in the system - mainly in the lines closest to the hot engine. The parts that can go bad and release pressure are the injectors, cold start valve, check valve at the main fuel pump and there's also a check valve in the fuel distributor.

I have a theory that maybe you could check out while you have the problem... I'm thinking the lines should be purged of the vapor lock if you hold the pedal to the floor while trying to start it. This should increase the flow through the injectors, purging any trapped air. If you feel like it, give that a try and let us know if it helps. Crank with it floored for say 10 seconds at a time or until it starts, whichever comes first.

Another thing that can help is to activate the fuel pump/s a few times before starting - just inserting the key and turning to ignition-on should activate the pumps for a second or two. Another trick is to hit the electric mirror adjust switch if you have elect. mirrors - for some reason that activates the fuel pumps in a lot of 924s with elect mirrors.

The real fix is to replace whatever's leaking, but there's a work-around involving the addition of a switch to manually operate the cold start valve. The instructions for that are in the FAQ.
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"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[Neil924]

Paul said you shouldn't use the gas pedal to start our cars ever. I can't remember what it may damage but....

[timstar92404]

if you press the pedal you might cause a backfire like it happened to me a week ago and blow off hoses or possibly damage the air sensor.


I made a cold start valve switch that causes the cold start valve to spray extra fuel when you press the button (its not suppose to spray when the engine is hot). It does help start the engine but its not a fix but just more of a temporary solution. At least I don't have to wait 30 mins to start my car.
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78 924 sold.
85.5 944

[Paul]

The pumps only run a few seconds while you are cranking it....

Cranking it longer than the pumps run is useless.
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White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

[Smoothie]

No, I don't think so. If you only switch the key as far as ignition-on, the pumps'll run for just a couple of seconds. -But in start, the engine's turning and spark's being generated, the spark's telling the fuel pump relay that the engine is running and the relay keeps the pumps switched on.
I know they keep running on my own car because on a rare occasion I get what seems to be the hot/warm start problem. When I do, I stop cranking, then try again with the pedal to the floor. It hasn't failed me yet and the car starts within about 5 seconds and without backfires.
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"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[plyhammer]

When this occurs to me, the car doesn't even crank???? The gauges work and all like it is going to start but then nothing, no click, just nothing. After an hour or so it works? This last week I got stuck on the side of the road and it never came back, I had to pull start? HELP!

[Smoothie]

Oh, that'd be your starter solenoid then. I've gotten into the habit of removing mine for a cleaning at least once a year. They tend to get gunked up with grease and dirt, then stop working when they're hot. I'd recommend getting a new solenoid, then pull the starter, replace the solenoid and clean and keep the old one on a shelf for possible future reuse.
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"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[Paul]

Might be different on some of our cars, but on a 80 931, I believe the fuel pump relay times out after a few seconds of cranking since it does not see enough rpms from the coil.

[Smoothie]

Could be.
I took a look at the '82 924/924turbo owners manual and it actually says - "When the engine is hot, fully depress the accelerator pedal while starting." and "If the engine fails to start after 10 to 15 seconds of cranking, wait about 10 seconds before restarting."
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"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[numbbers]

OK, getting back too the original problem. Yes, this sounds like the hot start problem, and this is one of the few areas where I disagree with Smoothie. Vapor lock can cause a hot start problem, but it is not a common problem in these cars. Go to the tech section, and read the FAC on the hot start problem. It will link you to the hot start problem fix. I wrote the article, and the fix is still working on my car after 15 years. On a recent 105 degree day here, I had to use my hot start switch for the first time in a few years, and the car started right up.
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1980 924 Turbo

[plyhammer]

So, since mine doesn't even crank it is probably the selonoid? Does this sound right?

[Smoothie]

Yes. Quit stalling and swap that solenoid.
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"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox