GetBoosted

Hi all,

I have a 1981 Porsche 924 and I went around a turn and there were some typical PA potholes on one side that I went over slowly since they couldn't be avoided and the car stalled. It wouldn't immediately restart but after about 5 minutes it fired right up.

So I went on my way and then on the way home from where I needed to go, I went over some uneven road (road before some train tracks) and the car felt like it wanted to stall again... it didn't but it felt that way since the revs dropped down to near zero and it sputtered.

I was doing research and it sounds like that could be the result of a bad DME relay or a bad DME. I was thinking about picking up a new DME relay just to see if that fixes it but I figured I would get some other opinions to diagnose the issue so I know what the issue is before I just start replacing parts.

Thanks!

fasteddie313

Hey GetBoosted is it a turbo 924? If so it sounds like a flaky DITC ignition connection maybe, check the connections to the ignition box behind the radio area if its a turbo and/or the ignition box mounted to the front inside of the drivers side fender under the hood.. Or maybe a loose coil wire.. If it is a turbo it sounds like it could also be the overboost switch..


I believe your shooting down the wrong path with the DME stuff because an 81 924 of any sort should have neither a DME relay nor a DME, It should not have electronic fuel injection like a 924S or 944 but rather a bosch K-Jetronic constant injection system (non-electronic, no computer).

So your 81 924 is significantly different from the other cars here in regards to its engine and fuel/ignition and much less prevalent here compared to the newer cars.
924board.org is much more specialized toward the older 2.0 cars and you may do well to search and ask there also..

But yeah anyway, it does sound electrical, check all the electrical connections you can find, clean and reinstall all the grounding points you can find, make sure your engine block ground is good, alternator ground, things of that nature..

morghen

hold on, if its an 81 its not a 2.5L, show us an engine bay pic of your car.

GetBoosted

Thanks for the replies guys. I'll reply individually below...

No turbo here :-(. Just a plain jane clean 924. As far as having the relay, in the relay diagram I've attached it does show a relay at position two which I was thinking could be the problem. Not a DME relay though so my apologies... it's the fuel pump relay. However your point around potential ignition electrical gremlins does make sense since it's more of an immediate cut out versus a fuel starvation type of stall.

Thanks for the pointer on the 924 specific site as well. I will check that site out as well.

Please see attached. Just snapped a shot to show the engine bay.

morghen

Replace relay from position 2 with a new one, or refurbish the old one.

mytrplseven

If this doesn't work, check AFM, TPS, Ignition coil and ground connections for security.

ideola

It sounds like something in either the ignition circuit or the fuel pump circuit is getting interrupted. You should prepare yourself to diagnose this the next time it occurs.

Buy an inexpensive spark tester (similar to this one). The next time the car refuses to restart, use the spark tester on the MAIN COIL WIRE that goes between the coil wire and the ignition distributor cap. Remove fuel pump relay (to avoid washing fuel down the cylinder walls). Crank engine. If you have good clean spark, then the problem is most likely in the fuel pump circuit.

(This, by the way, is a good example of basic troubleshooting...take the whole problem, break it in half, and conduct a test that will eliminate one half of the problem. Continue doing so until you've isolated the culprit).

It definitely sounds like an electrical fault. One of the things I've seen is that the spade terminals on the back of the fuel pump relay can come loose and begin to work out of the relay holder, causing intermittent contact. This kind of fault can happen anywhere in the fuse block, so I would pull that down and pay special attention to all of the relay terminals, making sure they can't be pushed out from the front side (or pulled out from the back side) when inserting the relay.

Of course, there can be a plethora of additional electrical faults, including frayed wires at the coil connection, frayed wires at the positive battery post (check those really carefully!!!), wiring faults in the main alternator/starter harness (you should check these as a matter of course, as they are frequently destroyed on the non-turbo cars due to their proximity to the exhaust manifold), bad wiring to or at the fuel pumps, etc.

The key to troubleshooting this is to take a methodical approach, keep breaking the problem in half until you find it. Also, don't assume there is only one problem. It is not unusual to have multiple issues compounding the matter, or you may find things that appear suspect but aren't actually causing the fault (case in point: burnt up alt/starter harness).

GetBoosted

Thank you very much for the help guys. I ordered a new fuel pump relay today so once it comes in I can toss that in there or keep it as a spare if I find that the issue lies elsewhere.

In the meantime, that's a great idea to keep a spark tester in the car so I can check it the next time it comes up... I'm going to toss that & my multimeter into the glove box for the next time it happens. I'll also take a look at the fuse relay box as well.

I'll take a look tonight to see if I can pull the fuse panel down so I can take a look at the wiring behind the relays to see if there are any glaring issues back there as well.

I didn't know about the potential to have issues w/ the wiring around the alternator & starter but that does make sense... I'll check these as well. I already went over the battery wires & those were looking solid as were the coil wires & plug wires when the car stalled before. I'll take another pass at them though just because I was checking on the side of the road & it's possible I missed something.

fasteddie313

Your name GetBoosted made me think it was likely a turbo..

A very immediate cutout like that sounds like a symptom of the common cracked ignition switch housing..

Perfect thread for that,,

http://www.924board.org/viewtopic.ph...ae93a4450ff3ed

GetBoosted

Ahh sorry for the confusion. The name is actually a carry over since I typically go for turbo cars. And it fits with my other car, a 996 Turbo.

Thx for the share on the other thread. I'll have to check that too.

morghen

Your 924 looks very good! so does your 996
Did you think about converting the 924 US bumpers to ROW bumpers?

GetBoosted

Thanks! I haven't considered that but those bumpers do look very nice so perhaps at some point.

GetBoosted

Took a look over the electrical components today and found that one of the clips on the distributor (the one behind the distributor between it & the faux firewall) had come loose & was making the distributor loose. Took the car for a spin through some back roads after fixing and so far so good.

Thanks for the help everyone! I'll report back if the issue comes back.

GetBoosted

Turns out I was wrong & the issue did not go away after resolving the distributor cap issue. I just wasn't going fast enough apparently. Found that the issue is still there when I'm on a road where I can open it up a bit further. Going highway speeds of 60+ I have found that when I go over really bumpy parts in the road. At highway speeds it doesn't cut out though which is nice... just attempts to stall which is not great and the tach goes really high then drops to zero then flutters back to normal.

Also noticed that after the car is warmed up, I can only take it above 5k RPM when its in neutral. While I'm in gear and I hit 5k RPM it feels like I am hitting a brick wall and it attempts to stop. It's weird... it's like fuel cut or something.

My new DME relay arrived so I'm going to put that into the car as a first step and report back but I'm guessing that is not going to resolve it since I'm just not that lucky it seems :-). Going to re-check all the grounds as well to make sure there is no hang up there too.

morghen

hmm, i wrote you about how to check the fuel circuit near the pump and replace the pump but if you say that the tacho bounces then its probably on the ignition side.
I had a bad ignition module once on my 83 NA...source a good one and give it a try.