92 4.9L
--fuel pump went dead. I banged on the pump and wiggled the wire harness for a minute and it started up and ran long enough for me to drive it home.
Died again at the store.
I ran a test on the wires...got two out of the five to read hot. Very weird readings though...the red wire hit something like 166.4...didn't even make sense (volt meter set on fused 12v)
Second hot wire ran somewhere around 4.7.
I picked up a new fuel pump but now im starting to wonder if it's actually just my wiring that's going bad.

Next step i suppose is to run a 20a fused wire from the battery to the fuel pump and see if it runs. I rotated the three relays in the power box also to see if i had a weak relay...didn't help.
The truck has had throttle response and acceleration problems...running lean...basically starving for fuel and i have suspected the pump for at least a month....DOES ANYONE have some input--bad pump???

Well, i cannot find the wiring diagram and specs for voltage, etc for the 5 wires going to the pump...any help?? Much thanks

 

Being you said red wire I will take it you have two fuel tanks.
So it should be wired like this:


/

 

Thanks Subford. I must have a weak supply between the relay and the pump then. I've heard the inertia switch can sometimes be a weak link.

 

Running that fuel pump power supply test worked great. Saved me some time--after installing the new pump, truck is running better than ever before.

 

Even though this is an old post I would like to thank everyone it. I found that that i had selector switch hidden behind my dash that went bad. I wired the rear tank and rear gauge so that it was the only one that would be used.