Fuel pump relay ground.

[EnthusiastMan]

Hey guys, got a quick question. I have an '89 S13 with an S14 SR20DET swapped in. Everything is wired up and I'm getting everything I'm suppose to except for fuel. I've sourced the problem to the fuel pump relay ground. There is a black/pink wire that comes from the relay and runs back to the ECU harness. When I manually ground this wire the engine cranks up runs good. I've searched all over but can't find any loose ground wires. Does this wire route back inside the car or does it stay inside the engine bay. Thanks for any help.
Modified by EnthusiastMan at 6:47 AM 3/24/2007

[EnthusiastMan]

Update: I've found where the black/pink wire runs. Apparantly somewhere in the ECU harness the wire changes from black/pink to black/yellow. However, I have another dillema. When I hook my voltmeter to the black/yellow wire at the ECU and turn the key on, I get battery voltage. When I ground this wire out it kicks the fuel pump on. I know this is the way it's supposed to work but when I ground the wire out the fuel pump keeps running and doesn't stop. Normally they are suppose to run for 3-5 secs and then shut off. Also, if the ECU is providing battery voltage to this wire, what is supposed to ground it? I thought that the ECU would ground it because it's only supposed to be grounded for 3-5secs. This is very confusing.

[vancouverbc]

The ECU supplies the ground when it wants fuel pump on. It will supply grund for first few seconds but if car does not start it obviously is going to stop supplying ground. So, the ground wire is going to a terminal on the ECU.

[EnthusiastMan]

Thanks for clearing that up. I have another question though. Why is the relay supplying 12V's to that same wire that the ECU grounds. When I hook a volt meter to the black/yellow wire at the ECU it has 12V's. When I ground it out, it kicks the fuel pump on.

[vancouverbc]

Thanks for clearing that up. I have another question though. Why is the relay supplying 12V's to that same wire that the ECU grounds. When I hook a volt meter to the black/yellow wire at the ECU it has 12V's. When I ground it out, it kicks the fuel pump on.

ground equals 12v negative. you need both negative 12v and positive 12v to have 12 volts. voltage arises from the reaction between positive and negative. grounding the wire is suppling 12v negative to the relay. I dont know what procedure you used to measure voltage at ECU. I assume you hooked up the ecu wire to a 12vpositive source. if you hooked ecu wire to 12v negative(ground) and you got 12volts , then you are saying ecu wiring is 12v positive which would be a puzzle.