In a real pickle with fuel pump issues. Advice appreciated!!

[jj3393]

So you're saying the pump primes with the key on before you crank it, but the pump doesn't run when it's being cranked?

If that's true and the pump primes with key on, what kind of pressure is at the fuel rail (without cranking it)?

If you have jumper cables connect to battery negative and to the GROUND connection on the alternator bracket; that will test for a good engine ground. You could also move that test connection to one on the body at the firewall, but I'm not sure body ground is an issue.

No. The pump won't turn on or prime at all during any of this. Also, using the connector ground during testing.

 

[Fless]

Just out of curiosity have you checked the PCM-B fuse that is next to the fuel pump relay? Pull it out and make sure both legs are intact and it's not blown and has good tension on the blades.

 

[jj3393]

The 20A? Yes

 

[Fless]

Have you tried banging on the underside of the tank while the truck is being cranked?

 

[Fless]

The only other thing I can think of would be wiggling the ignition cylinder somewhat as you turn the key. Pick up on the key cylinder a little in case it's worn. Other than that, checking the voltage on both sides of all critical fuses like for the BCM (the inside left panel fusebox holds at least 3 TBC fuses).

 

[jj3393]

Have you tried banging on the underside of the tank while the truck is being cranked?

Haven't done this. We are also only hooking up connections while fuel pump is out of tank. The tank is dropped, but we removed the pump from the tank itself while testing harness connectors

 

[iamdub]

I'm understanding this as you have 12V and ground at the vehicle harness (unplugged from pump's connector) for a few seconds when you turn the key on (priming). But, you don't get voltage when it's plugged into the pump's connector and turn the key on again to prime. If you unplug it and check for voltage again, it's there. Is this correct?

Do you get 12V and ground when cranking (still unplugged) ?

Screwy things happen with low voltage. After it sat for those few weeks, was the battery low when you first went to start it?

With the pump installed (any of them) and the tank in place, did you connect the ground on the filler neck to the body?

 

[jj3393]

The amperage goes down when trying to crank. Also did not connect filler neck during any of this. It's primarily just trying to get power to the pump once connected. The harness' have power, but once you plug the pump up, it doesn't power the pump itself

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

You are already receiving sage advice from the knowledgeable folks on this Forum. They will help get you through this issue.

 

[Mudsport96]

Ok so how did you determine power at the connector?
Did you probe the connection from the back side or did you push the meter leads into the pin side of the harness?

If you did the front side, it is possible that you spread the terminals enough that they dont make contact with the pins on the pump side of the connector.
Second, if you have the clamp style meter, pull the wires out of the loom enough to get the amp clamp around the positive wire. Then key on to see how many amps are being drawn. I have seen 12v at the pump but corrosion in the harness caused an amp drop not allowing the pump to actually run on one of my own vehicles.