At work I have been handed somewhat of a basket case. I am working on a 61 Corvette that has an LS1 out of an 04 GTO. It is running a combination of a universal painless wiring harness and the factory GTO one. It is also running a set of Dakota Digital VHX gauges. I am having a really odd problem out of the fuel pump relay. The part that makes it odd as everything has been functioning just fine for the past two months. I got in it this past week to move and started it up. It ran a couple of minutes and died.

The DD gauges are powered by the OBD port. With them plugged in the fuel pump relay constantly just clicks. Right off I thought bad relay and threw a spare I had in. I left the gauges unplugged as I hooked HP Tuner to the car to check on something else and all was good. When I plugged the DD gauges back in the relay started clicking all over again. I tested the new relay and old, both are working like they should. The connector wiring was function tested and seems fine. *Test light, not multimeter*

I have come to the conclusion its some type of grounding issue between the PCM and the DD BIM interface. I have checked all of the connections on the DD boxes and have attempted to locate some other grounds to check them and so far all seem good. From what I have read it seems the PCM doesnt have a good enough ground to hold the relay closed... but it does have a stong enough ground when the DD gauges are unhooked. With the gauges unhooked the relay functions just fine and the car starts and runs just fine. With the gauges powered and the relay clicking; the car starts but stumbles dies as the relay is turning the pump on and off not feeding the motor.

My knowledge of a multi-meter is very low as I am a Auto Body guy that dabbles in mechanics. So if you ask volt or ohm checks/ numbers I couldnt really tell you. *I have been reading up on how to use one on another window tab*

I am just hoping someone has had an experience similar with a simple fix that I have looked over instead of me tearing this car back apart chasing wiring.

 

Check that all of the ground ring terminals in the engine harness are bolted tight to the block. The block should also be grounded to the frame with a decent sized cable.