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928 S4 Starting Trouble


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Greetings fellows,

Saturday i bought my first Porsche, an `89 928 S4 autimatic. Tested it and looked through all parts before i bought, and started it approx 10 times before i paid. No problems. The engine was then warm all the time. Drove it home, 500km without any problems. Happy camper.

Sunday i started it up in the morning, no probs. Drove it to a nearby gas station(6-8 minutes) and washed it outside. When i was finished it would not start. The starter engine runs fine, but the engine will not start. Tried a lot until there was no more battery. Removed the plugs and they was as a result of my trying, wet in fuel. Replaced the plugs with new ones and tried again(with battery power from another car) but it would not start. Then i waited until dawn(6 hours) and tried again. It started and runs fine. Drove it for 1 hour to be sure there was no problems. I then assumed something got wet in the washing process, and i thought this would not happen again, so i was not that concerned.

Today, monday, it starded fine in the morning again. Drove it to the gas station and washed it inside. AGAIN, not starting afterwards. Not fun. I am now waiting for the engine to get cold so i can give it another try.

My conclusion is that it starts fine cold, and fine warm. But after a short trip and a little wait (1/2 hour) it will not start.

I can mention that fuelpump, waterpump and rotorcaps were replaced 25000km ago.

The person i bought it from says he had a little starting trouble when he first got the car, but after this he have started the car with the gas pedal half to the ground. He claims that with this he never had any problems. He told me this after i got the troble and called him so i did not know about this when i bought it. I have also tried this when it will not start, and it does not help.

Anyone have any idea what the problem might be?

Thanks, from a little disappointed first time Porsche owner


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stop washing the car!!!! just kidding.

check the coil wires themselves, check and replace the DME relay. also the DME and LH control unit are located in the passengers kick panel. make sure they are not getting wet when the car is washed. the fuse box is under the wood panel on the passenger floor board make sure it is not wet either.

under the hood near the fron of the car, I can't remember exactly but follow the wires from the coils. are 2 final stage boxes. make sure water isn't getting in to them either

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  • 1 year later...

Im with magcuda the LH and/or DME might be getting wet after washing(Water leak at the base of the windshield). I would look under the hood and check the passenger floorboard area after washing to see if you notice any traces of water intrusion. If im not mistaken the coils on the 928 are on the inner fenders so make sure no water is making it around any water seals the hood may have.

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