Fuel pump wiring

[danny never]

My fuel pump is not coming on. I checked the inertia switch and swapped the relays to no avail. I want to run power directly to the fuel pump to make sure its bad before I swap it. Can't find a wiring diagram anywhere for the fuel pump. I dropped the tank already. anybody know which of the 4 wires coming directly out of the fuel pump are hot and ground to the fuel pump?

Thanks!

 

[budwich]

well... just go back to your inertia switch and put battery right "after it" (PK/ BK)... that should check your wiring without dropping the tank ... :-(

better yet, put a meter on it and read the resistance.

 

[danny never]

Thanks!

which one is positive? (sorry, I'm more of a motorcycle guy)

 

[danny never]

update:

I disassembled the fuel pump sending unit, and applied 12v directly to the pump itself, it came on.

I checked voltage at the inertia switch, I get 1.5v constant at the green/yellow wire, nothing at pink and black, (its unplugged) and 11.5v at the gray/orange

 

[danny never]

At the plug in front of the fuel tank, I got
Green/black 2.4v
Black/yellow 0.02
red 0.02
black 0.01
yellow 11.5v for 2 seconds
pink 2.5v

at the plug that plugs into the fuel pump/sending unit, I got

pink/black 1.5v
yellow/white 11.2
black/yellow 0
black 0

 

[budwich]

with your key turned to ON, you should see ~12V coming in to the cutoff switch on the DK/Y and leaving on the PK/BK towards your pump. It will only be there for a second or "two" since the PCM drops the relay (fuel pump relay) to stop the pump if your motor isn't running. During that time you should hear your pump run.

 

[danny never]

Ok, I ran 12v to the pk/bk and heard fuel pump. I checked DK/Y again, (dark green/yellow right?) and only get 1.5V constant.

 

[budwich]

OK.... well, then you may have a common fuel pump relay problem (or area around there). Use your meter to check at the fuel pump relay... one that it operates and two that voltage is leaving the relay on DG/Y. Note this will only happen for a second or "two" as the pcm drops the relay if the engine doesn't turn.... so you have to be quick to "listen / look". Note also you don't have to try to "start", just turn the key to ON. Note also, if you have run your wire to get the pump to run.... with the jump wire installed, try starting your truck, if it works then you are "almost there". If not, then you know it ain't a fuel problem.

 

[danny never]

budwich, thanks so much for your help (and patience) so far, I really appreciate it.

It started up with the jump wire, so I'll do some checking around the relay area this weekend.