Question about 1992 Porsche 911

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Cranks fine but will not start

I am actually a mechanic but this would be the first porsche i have ever worked on, so dont hold it against me. I have tested almost every circuit that goes into the computer and everything seems to be working, the engine cranks but will not start, it does not have any injecter pulse, no spark, and no fuel pump operation. I have already tried a new computer and i am still getting the same issues. I have also tested the "Digital Motor Electronics" relay and it is working the way it should be, the computer is getting all of its power and grounds, i checked everything with an ohm meter. The crank sensor is sending about 4 volts to the computer while cranking and from what i have read that should be more than enough. As far as the fuel pump operation goes I can ground the the wire that controls the fuel pump relay right at the computer and it comes on and works fine. I was thinking about the security maybe disabling the engine but i have no way to test the security, we do not have the equipment at the shop to test it. I have also noticed that every once in a while the battery will go dead over night, I have not really got into that problem too much, I am more fixated on getting it running. I have talked to a few people about this and nobody seems to know a whole lot about porsches, any ideas would be very helpfull. thanks

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I don't know much about Porsches either, but the only thing I can think of is the Immobilizer system not recognizing the key and not letting the car start. I don't know if Porsche even had that in 92. But if the key is thicker/bigger then the regular keys, then it has Immobilizer. Then I would look for instructions on how to program the key to the car (that's assuming the system is working fine and it's just the key that's new to the car or the system's memory was somehow cleared).

Posted on Jun 17, 2009

  • Mohd Sameer Aug 30, 2013

    i have the same problem after chaniging my Cayenn engine , it starts on works as soon it is connected to the computer but it wont start again as soon as i turn the engin off , i need an answer for the ,,, i fel it is something with memory of the computer ????????



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