Recently got all the wiring done and got the base tune on the pcm on my 87 fox swap. . Now I turn the key on and the fuel pump comes on like its supposed to. Key off and keys sitting in passenger seat, turn headlight switch on and bam fuel pump comes on. WTH, the only common point the circuits have between each other is the ford starter solenoid. Its acting as a lug until I can get one. Not sure what could be going on. Any ideas?

 

Had the same problem on a 92 notch swap. Make sure the grounds for the head lights and main harness for the car is good.

 

Thanks Ill check into that. I know the headlight harness has the 2 spots on the front that ground and not sure where the main body harness actually ground at. Maybe by the pcm.Ill have to trace some.

 

Sounds like a shared ground issue.