No power to fuel pump (1 Viewer)

[workingdog]

I posted this on Hardcore, but there's not much life over there, so I'm posting here as I am totally stumped by this.

First - this is a 2005 5.3/4L60 with a Howell harness. I didn't do the conversion.

The fuel pump isn't running.
I jumped the fuel pump at the relay, it works.
I've got no +12 at the orange wife (always BAT 12) fuel pump relay. after the relay, all the wires dive into harness and I have no idea where the power for the relay comes from.
I've check all the fuses in the cab and I can't find any other fuses that might be causing the trouble.
I've got BAT +12 and switched +12 to the Howell fuse block.
But not +12 at all at the fuel pump relay. 0 volts at orange wire on relay block that should be BAT +12.

I need some help on what to try next. How can I tell if the ECM is alive? I can hear the relay cycling through the fuel pump priming cycle.

Is the constant power to the relay coming through the computer, or direct from the battery through a fuse?

 

[mattressking]

I posted this on Hardcore, but there's not much life over there, so I'm posting here as I am totally stumped by this.

First - this is a 2005 5.3/4L60 with a Howell harness. I didn't do the conversion.

The fuel pump isn't running.
I jumped the fuel pump at the relay, it works.
I've got no +12 at the orange wife (always BAT 12) fuel pump relay. after the relay, all the wires dive into harness and I have no idea where the power for the relay comes from.
I've check all the fuses in the cab and I can't find any other fuses that might be causing the trouble.
I've got BAT +12 and switched +12 to the Howell fuse block.
But not +12 at all at the fuel pump relay. 0 volts at orange wire on relay block that should be BAT +12.

I need some help on what to try next. How can I tell if the ECM is alive? I can hear the relay cycling through the fuel pump priming cycle.

Is the constant power to the relay coming through the computer, or direct from the battery through a fuse?

Two courses of action:

1. Get a diagram for the harness to understand where the +12v for the fuel pump relay terminates at the other end.
2. Take your voltmeter and test continuity. There shouldn't be many to test in your harness from the fuel pump.

Once you determine which wire connects to the +12v to fuel pump relay on the other end of harness, begin working backwards. Continuity is the easiest way if you don't have a flow diagram.