1989 porsche 928 will not start

Hello, I have narrowed the problem down to the fuel injectors not getting power. the LH ECU has been replaced with a rebuilt one from JDS porsche, internel and external fuel pump has been replaced same as fuel filter. the car sparks, when i put a noid light in the fuel injector harness it does not flash or turn on at all. any clues or steps to finding out where a short it?

1989porsche928;91 wrote: the LH ECU has been replaced with a rebuilt one from JDS porsche

I would expect John (of JDS) would be very able to advise you, have you emailed him with your issue?

1989porsche928;91 wrote: ...when i put a noid light in the fuel injector harness it does not flash or turn on at all...

Then you're most definitely correct. No voltage. The first thing I would do is have a helper turn the key over while you stand at the back of the car and listen to see if the fuel pump is being energized. If not, then jumper the relay for the fuel injection ecu and try again. If you have success, then all you need is a replacement relay. If you still have nothing, check your grounds. If these simple checks don't get you anywhere then report back to this thread and we'll go further with some more detailed troubleshooting.

i replaced the pump after it didnt start so the pump was bad and now it still wont start, both internal and external where replaced, i can here the pump, i can here it run continuasly when i jump it the relay.

If we're talking about an '89 model then it has always been my understanding that there is just (1) external, in-line fuel pump. If you're absolutely positively sure that you're hearing the pump being energized then you certainly don't have a power supply issue to the computer. You must have a break in the injector circuit or there is a fault with the computer itself.

Let's start by doing a resistance check on the entire circuit. Measure resistance of plug "X" on the CE board. Measure between terminal 8 and ground with a functioning ohm meter. Report back with the figures ASAP.

Do you mean relay x to ground? like If I where to take relay x off and put a multi meter wire in one of the sockets and the other one to ground? do I need to disconnect the battery?