924Board.org

[FHJ]

Hello everyone,

I'm new here, thanks for letting me join, I noticed there is a lot of knowledge here.
So I'm Dutch, I own a 1979 924 2.0, 67.000 km original.
Since a year the car has a really weird problem, it starts up like a brand new one, runs perfectly.
Only after some time (mostly after approx. 45 minutes) it stalls.
If running stationary, outside the garage it's really after approx. 45 minutes.
When driving it stays kind of ok, recently I drove it to a friend, 20km away and git there and back home without a problem.
Yesterday I took it for a drive and after a while I noticed it did not respond well to the accelerator.
When I pressed it in, the engine hesitated. Pressing in the clutch and then revving it up keeps it running if that happens.
Then I drove it to the McDonalds to get an icecream fir my daughter who was with me.
Waited in the mcDrive (so a lot if stationary running), when I wanted to drive off, the engine didn't respond to the accelerator and died.
Normally, after waiting some time, like 10 minutes, it would start again, but not this time.
Towed it home, 10 minute drive, and surprisingly it started without hesitation.
What happens here..?
Been struggling with this for over a year now.
Replaced fuel filter, checked both fuel pumps, replaced the ignition coil as it git quite hot.
Checked the WUR, looked like brand new inside. Checjed the cold start valve..
I don't think it is the well known hot start issue, because the engine really dies after a while, it is not that you can't start it after turning it off.
It loses power and then dies.
But why only after 45 minutes.
I also jump wired the fuel relay.
Btw, after trying to start it again, it smells of fuel, like it's too rich.
What can this be, faulty injectors maybe? After running stationary at the mcDrive maybe too much fuel dripping inside the cylinders?
Any views on this would be highly appreciated!

[morghen]

I can offer an engine management system that looks nearly identical to the original k-jet.
You can fit it yourself or have it fitted by a specialized shop in the Netherlands.

Check out my website (link in my signature) and also check out the garage/shop: https://www.garagedeloods.nl/
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Supercharger and EFI kits
https://www.the924.com

[Beartooth]

That's a tough one. The time factor makes me wonder if it's ignition-related - I see you replaced the coil, but maybe the ignition box causing a weak spark when it gets warm. The other thing that comes to mind is fuel starvation: maybe the fuel pump is marginal, or maybe the tank filter is gradually accumulating enough crud in that time to starve it.

Next time it does it, you could try pulling a spark plug or two to see if they look normal or sooty or wet. A fuel pressure gauge would also be helpful: when dies or is acting up, you could hook that up and see if it's got normal pressure. An inline spark tester might be useful: try it out with the engine cool, then again when it acts up.

The fuel smell doesn't necessarily mean it's fuel-related: if you're losing spark (especially if you're trying to rev it), then that could be throwing fuel down the exhaust. The injectors seem pretty unlikely to me. WUR is also unlikely, but maybe possible. It wouldn't be the first thing I'd check, but checking control pressure when it acts up could reveal something.

Of course, by the time you hook up the gauge, whatever it is might clear up, and driving around with them hooked up is iffy at best. Have you ever tried just letting it idle to see if it starts acting up after 45 minutes or so? If it did, that would be one easier way to help troubleshoot, but I know these things like to hide until an inconvenient time.

One other thing: does this car have a frequency valve and oxygen sensor? If so, I could see the controller being the cause, or maybe a wiring or ground issue with the valve itself. That would make the car undriveable. If you jump the fuel pump relay, you should hear the valve buzzing, so if it acts up, you could try jumping the relay and see if the buzzing is still there. But if it doesn't have that, disregard.
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1980 931 diamond in the rough