Stan944

This morning my 944 stalled while driving at highway speed. It's the first time it happened. Had it towed back home. Couldn't start it back. Ironically, the engine started this evening, so I have an intermittent problem (I hate this kind).

I'm not sure what to do now. I tried searching, and found a few similar case, but it seemed like the problems didn't get fixed completely.

Possibilities the way I see it:
1) electrical
2) fuel delivery

Actually, a few days earlier I couldn't start the car, but depressed the gas pedal while cranking, and it started.

I suspect I have dirty fuel tank (although I put a new fuel filter a while ago). I want to clean it. I think I should remove the fuel level sensor, and use a long brash to move dirt away through the (disconnected) hose to the fuel pump.
By the way, can I replace this rubber hose with a close SAE size?
Any hints on how to clean the fuel tank?

My fuel pump was buzzing for a few months now. Could there be some thermal fuse in it that engaged when the pump couldn't handle it, but "let go" after a few hours?

I should inspect the DME relay for half-broken solderings...

In any case, I feel rather desperate here, so HELP.
Thanks

ODUporschegurl

my car also stalled on highway last weekend. however restarted fine. it will be visiting dads shop @ home tomorrow(if i can make it the 3 hours)

hosrom_951

Try switching the DME relay, a rennlister on the Turboo and Turbo S board had his car stall when doing 140mph

Turned out to be a dying DME relay, try that first.

Stan944

OK, I'll get a new DME relay. I don't think I can get it in a local store, so I'll have to order it from a dealer. But since a weekend is coming (dealers don't work on the weekends), any advice for THIS weekend?

phil0618

Hi,

I had the same type of problem and did extensive research on the forum. The top three recomendations from our fellow rennlisters were (in rough order)
1. DME relay - some even suggest having a spare one around
2. Speed ref sensors
3. Fuel Pressure Regulator

My symptoms were 2
1. A couple times while driving at highway speeds the car just died for no reason.
2. I would drive the car long enough to get it hot (say 15+ minutes) then shut if off and then when I tried to restart immediately it would not start. Wait ten minutes for things to cool and Voila! it would start right up.

I replaced the DME and FPR at the same time and have not seen a recurrance of either issue.

Some have luck by tapping the DME with something solid a few times and some have had luck by fiddling with the ref sensor wires which I believe are near the firewall above the bell housing.

Best of Luck!

Phil

streckfu's

This happened to me and was caused by the speed ref sensors.

Since it restarted after sitting, it could those or the DME relay failing when hot and then working when cool.

Try both. DME relay iseasier and cheaper.

Chris_924s

I would suspect poor voltage at the plugs as well. Check your coil.

KLR

Very high probability that it's the DME relay, but, besides the above suggestions, it could also be the ECU itself. If tapping on the computer allows the car to start again the next time this happens, you have a cold solder joint in there and can usually address it by reheating all of the joints. I'd bet on the DME relay, though, particularly if it's still original. I carry two used spares that I know work just in case.

Stan944

Thanks guys:
After reading above, I think a good option for me is to install new:
DME relay
fuel pressure regulator
Afterall, my symptoms look like the beginning of what Phil saw...

Is the fuel pressure damper a suspect too?

Why speed reference sensor? The engine can run at stand-still. Or this is the jargon for the RPM sensor above the flywheel? I know there are two "sensors" that plug to the belhousing. Is it what you guys are talking about?

The coil? I don't think I know how to check it for intermediate problems. I guess next time it happens, I could unplug a wire to the spark plug, and check for the spark by cranking the engine. But I don't think I can do it alone (I commute to work all by myself), or there is a trick?

I could tap the ECU next time it happens.

streckfu's

Trust me on the reference sensors. I don't know the exact reason, but mine failed every now and then preventing the car from starting when warm. Let it sit for a couple of hours and it would start right up again.

I troubleshot it to them after trying the DME relay, testing the fuel pump, and pressure regulator.

I'm not saying that's it but try everything suggested. One of them should be your culprit.

Stan944

Daniel: ..just to confirm, you're talking the two sensors that plug at the top of the bellhousing?

streckfu's

Correct. Unfortunately, they are expensive so see if you can borrow a pair to troubleshoot instead of buying them.

Stan944

Do I need some sealing compound, etc. to replace this pressure regulator, or it's just to mount in it after releasing the fuel pressure?

Stan944

Took it for a ride. Worked fine for 15 min, I stopped, and 15 minuted later I tried starting the engine - no luck... Repeated - still no. After 1 hour it started OK. Couldn't reproduce the problem in the garage when I got home.

Der Rennwagen

I had the exact same problem you have on my early 1985 944 too. You would be driving along fine then nothing. Tach drops to zero and it won't restart. Wait an hour or so, fires right back up like nothing ever happened.

I did these items and it seems to have fixed it.

1. Replaced the DME relay with a new one.
2. Replaced the ignition switch with a new one.
3. Used dielectric grease and cleaned up the contacts on the 9-pin connector in the engine compartment above the brake booster. This connector services the fuel pump among other very important electrics.
4. Changed out both reference sensors with good used ones.
5. Replaced coil with a new one.