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

[jj3393]

EDIT: SPRAYING STARTING FLUID IN THE THROTTLE BODY GETS IT TO CRANK FOR A FEW SECONDS.

This is for a 2004 GMC Yukon 5.3 (Flex fuel). Working on what was thought to be a bad fuel pump. Vehicle was purchased, then driven 120+ miles to destination. It was parked then not touched again until now. Sat for a couple weeks. After all the ok driving and no issues, now it won't start. Diagnosed (from others) as a bad fuel pump. Have been through 3 brands of pumps, and no matter what none of them will prime or turn on at all. Have checked female adapter multiple times. Getting around 12V. Relay is good. Ground seems to be good. Everything has power until hooked up. Nothing is working. It's becoming a headache. Anyone else with this issue? Also, sometimes it will turn over and start to run then dies immediately (fuel pump still doesn't cut on)

 

[S33k3r]

Sounds like a security lockout. Might look for a kill switch somewhere. And, as always, a code reader might help (it might not, though). Also, the wiring at the gas tank it self could be causing an open in your circuit. Did you replace all the wiring at the gas tank?

 

[jj3393]

We have a computer to check. When we try to start it the immobilizer symbol comes on for a second then off, but unsure of the security part. We've asked if it got messed with. The answer was no, but it's funny that it ran perfect before. A long trip at that. Then one day it just didn't crank. I have no clue where this switch would be..

 

[Fless]

Does it always turn over (crank)?

If so, start simple. You can rent a fuel pressure test kit at just about any name brand auto parts store and test the key on, engine off fuel pressure. Alternately you can also do a simple test at the same schrader valve on the passenger fuel rail with a rag and a small screwdriver. Put the rag over the valve and depress the valve (it's like a bicycle tire valve, but larger) and see if the fuel shoots out or just dribbles.

If the fuel pump does not turn on for a second when the key is turned on (not cranked) then you might swap the fuel pump relay with another one that is the same (some of the others in the underhood fusebox are identical).

 

[George B]

How are you determining the pump isn’t priming? Pressure gauge?
Can you force the pump on with the fuel prime terminal under the hood of it has one?

 

[jj3393]

Actually have done all that as well. Even with the original pump, there was no pressure period. Though the new one is in there it seems that none of these pumps are getting power once connected. They harness (male) reads 12V

 

[jj3393]

How are you determining the pump isn’t priming? Pressure gauge?
Can you force the pump on with the fuel prime terminal under the hood of it has one?

There's two of us. The sound is prominent obviously once the key is turned over. We've both been beside the pump during the "attempts to crank" and not even a whisper of a sound.

 

[Fless]

For your voltage measurement are you reading the ground on the connector, or using a chassis ground for your VOM connector? Must use the connector ground.

Swapped the fuel pump relay with another as a test? Pick another identical one and swap it in the fusebox. EDIT The DRL relay right next to the fuel pump relay is the same; could swap those two.

 

[Fless]

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.

 

[jj3393]

We have swapped relays. All are in good working condition. Nothing of this makes sense. Like I mentioned, everything has power. Relays, harnesses, ect. Primary problem is basically the power to the pump disappears once connected to the power supply harnesses.