The 510 Realm

Over the last year I've been helping a friend swap aVQ 35 HR into his 75 280Z. We purchased a wiring harness from a place called Z specialties that is basically a four wire hook up. At this point I am confident I have all the wiring done correctly but this is the problem we are having . To power the ECU the wiring company suggested to pull 12 V from the ignition to a relay. Using a multi meter with the key in the on position we have 12 V before and after the relay . When cranking to start the engine the volts drop to zero . The engine did fire twice last night but that was it .

I assume some of the wiring harness is similar on the Z cars , and I know a lot of the 510 people here also are knowledgeable about Z cars. Does anyone know why the volts will drop during cranking ?

We have ran a ground from the negative post on the battery to the body and also tried to starter a bolt thinking it could be a bad ground but that did not solve the issue . Any ideas or suggestions would be greatly appreciated, thanks

Wait so did you try hook the suggested key power wire straight to the battery? Seems like you have it hooked to the wrong position on the ignition.

icehouse wrote:Wait so did you try hook the suggested key power wire straight to the battery? Seems like you have it hooked to the wrong position on the ignition.

We did , it would start run for a few seconds and die.

from memory some older ignitions took away power from the acc position while in starting position.this might be the problem?

maybe give the ecu power directly from battery power(through a fuse) as a test just to see if it solves the problem.
Nissan ecu's also need a start signal, just double check that it is present when needed.

Thanks Heinrich, this helped me resolve the issue. I found a wire that had the volts during cranking and tied that plus my other wire to the same relay and viola !

Mods this can be deleted now.