green and white

[BigrobDog]

350 chevy 1990 tbi. green/white wire on fuel pump relay, truck only starts if 12v jumper is on this wire, i have a fuel pump relay diagram and gr/wh shown going to b2 on computer and no were else,can some body elaborate on how this green and /white wire works along with the relay and the other wires please.

[VetteVet]

Originally Posted by BigrobDog

350 chevy 1990 tbi. green/white wire on fuel pump relay, truck only starts if 12v jumper is on this wire, i have a fuel pump relay diagram and gr/wh shown going to b2 on computer and no were else,can some body elaborate on how this green and /white wire works along with the relay and the other wires please.

Well this diagram shows the green/white wire going to a1 on the ECM but there are other wires going to the relay as well. The black wire is the ground, then you have the red, orange and gray. I believe the green/white wire is power from the ECM to turn on the relay coil with the black ground wire. I also think the red and orange wires are the power wires for the fuel pump and the fuel pump prime. The gray wire is a sensor wire from the oil pressure sensor which will cut off the relay if oil pressure is lost.

When you jump the g/w wire you are overriding the ECM and kicking in the relay so you get fuel pump pressure. The F/P relay is in the top center of the diagram and the G/W wire is the very top wire going to a1 on the ECM Then below the relay and to the left is the oil pressure sensor and just below that to the left is a fuse on the orange wire for the ECM, so you might want to check that.

I might be wrong on this but it looks like that's how it works.