Porsche Enthusiasts Club Forum

I set off today and got half a mile up the road and the engine cut out.looked under the bonnet,couldnt find anything obvious so tried it again and it fired.after another half mile it packed up again and this time wouldnt restart.Called the RAC who came in 20 minutes.he found that there was no spark,checked all leads,coil etc.and decided it had to be the ECU.I didnt know where it was and Haynes was no help either but eventually he found it,tapped it and the car started.I decided to abandon my trip so he followed me home and I put it back in the garage! So whats the score with these things? can they be mended or is a new one required?

Don't know a great deal but any chance the flywheel sensors ont the back of the engine block are to blame. Had similar problem with mine and the AA got it started. still happens occassionally.

I have a 944 ECU kicking around if you need one, let me have your numbers, i only want back what i paid for it - £70

My first shot would be flywheel sensors as well. When it died & you tried to restart did the rev counter bounce off its stop? If it didn't it's either flywheel sensors or connections to them or the ECU. ECU's are fairly reliable these days even old ones.

Second thoughts does it have an alarm/immobilliser? It could be immobilised.

If you look on Clarkes which is a stickied link on the 944 page there is info on diagnosing non-starts.

what about DME relay ?

Thanks for the prompt replies you guys!RH944,the RAC bloke checked the sensors at the back of the engine in front of the bulkhead and said they looked ok.he put his fingers on the relays and asked me to turn it over and said he could feel them ticking so pronounced them ok.Jim,Im afraid I didnt notice what the rev counter was doing,I ll have to check that next time it happens.I have no alarm although there is an immobiliser.It was only after he tapped the ECU unit that it fired so it does point to that.Demonfish,I may well take you up on your offer,I ll look for the numbers tomorrow.Every time we exhibit at a show and give out membership forms to prospective members I always try to impress upon them the value of this forum and again I am able to prove that value.Thanks again and I ll let you know how this develops.

Almost certainly the DME relay. OK so it clicked - the car started and ran for a bit a couple of times so it would, wouldn't it? Tapping the ECU would have been coincidence I bet. I once had a sticky speedo and used to tap the dash which seemed to get it going, but the root cause was the sender wiring on the transaxle, so it can happen that way. Even if it is the ECU if tapping it temporarily sorts it out then it must be a dry joint which is repairable.

It's only 20 notes to replace and I'd say greater than 75% chance it's the DME relay.

Just ordered a relay.I ll try that first!

Let us know. My first 944 broke down on the test drive. The dealer fitted a "new" ECU (which was a benefit as it was an 86 car and he fitted a later ECU so it ran slightly more boost than it should have and was surprisingly quick because of that), but it intermittently cut out soon after and eventually refused to run completetly. I called the AA as in the intervening 2 days I'd driven it from Aberdeen to Poole and the AA man stuck a used Vauxhall fuel pump relay in and away we went. Because it was used he couldn't leave me with it so he followed me home and took it out and I went to the local Vauxhall dealer with the part number and bought another one. Problem solved.

"but the root cause was the sender wiring on the transaxle, "

Fen. Could you elaborate? I have this problem & the speedo seems fine. I've replaced the sender too which helped. But it still sticks sometimes up to 20mph. Then it wakes up. Unless I give it a thump.

Not massively I'm afraid. I lay under the back of the car and reached up to locate the sender on the transaxle. When I found it I gave it a wiggle and thought "that's going to be a pig to get out", but I didn't have time to do anything about it then. The speedo worked perfectly from then on. I assume it was a dirty/loose connection or that I repositioned the wiring slightly such that a fracture in it didn't cause a problem any more.

Thanks. Will try wiggling it a bit!

so far I ve replaced the DME relay with a new one and on my first test drive I got 10 miles then it conked out again.On trying to restart it the rev counter needle never moved.I gave the ECU a tap,then it restarted and I drove the ten miles back.since then I ve been on a 30 mile round trip with no problems so now I m thinking the connections to the ECU may be dirty or gummed up so my next job is to disconnect it ,give the contacts a clean up and try again!

If the rev counter doesn't move then it'll be either flywheel sensors or ECU. It could even be a temperature fault on either that only fails once warm.