No Power Grey Wire to Fuel Pump

[Caman96]

1- Truck no start yesterday/ramp trucked home.
2- Has spark/no fuel pressure(zero).
3-Replaced FP Relay, although both “click” when keyed on.
4- Ground wire from FP hanger cleaned/sanded frame and dielectric greased.
5- With keyed on, harness to fuel pump unplugged and using test light, middle purple wire(fuel gauge) has power, grey power to pump- no power.
6- Also, did the 30 to 87 jump with relay pulled, and still no pressure.
Don’t really want to drop tank yet, especially with 30 plus gallons in there.

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Such a sad sight.

 

[HotWheelsBurban]

1- Truck no start yesterday/ramp trucked home.
2- Has spark/no fuel pressure(zero).
3-Replaced FP Relay, although both “click” when keyed on.
4- Ground wire from FP hanger cleaned/sanded frame and dielectric greased.
5- With keyed on, harness to fuel pump unplugged and using test light, middle purple wire has power, grey power to pump- no power.
6- Also, did the 30 to 87 jump with relay pulled, and still no pressure.
Don’t really want to drop tank yet, especially with 30 plus gallons in there.

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Such a sad sight.

Yup it's never a good thing to see your metal kid on a wrecker....

 

[454cid]

What keeps power on to the pump? If the engine isn't running, it just primes and shuts off. I know people are going to say oil pressure switch, but I'm pretty sure I disconnected mine when it went bad, and started my truck.

 

[Caman96]

What keeps power on to the pump? If the engine isn't running, it just primes and shuts off. I know people are going to say oil pressure switch, but I'm pretty sure I disconnected mine when it went bad, and started my truck.

Thanks @454cid. Thing is I knew that too, but didn’t factor that in. I’m out there and I’m really not feeling well, sick with something. So there it is, it’s got the 2 second burst to pump and no good. I even double checked and ran 12v to grounded pump and she’s dead. 30+ gallons to be drained!

 

[Caman96]

Fortunately, I have a NOS sending unit paired with a NOS Walbro fuel pump. Question, does anyone know what part of harness on these original sending units had issue? Is it just the 4 wire harness that comes out of top that goes to power? I also ran a quick test on this setup and seems fine.

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[tayto]

The relay needs to be plugged in to test power to the fuel pump. also note with key on engine NOT running the relay will only be energized for a few seconds therefore power on the grey wire will only be there for a few seconds.

The oil pressure circuit runs in parallel of the fuel pump
relay. so either if either one is working it will supply power to the fuel pump.

 

[Caman96]

The relay needs to be plugged in to test power to the fuel pump.

It was, I was just performing test wrong. I’m running a temperature and @454cid set me back on track! So, it does have power and I believe pump is dead after running dedicated power to grounded pump. What about that those original harnesses, you know anything about those, was there a TSB?

 

[xXxPARAGONxXx]

Bulletin (attached) only applied to fuel pumps with an Aptiv-Delphi Metri-Pack (M/P) 150 connector. It would need to replaced with an Aptiv-Delphi GT 280 connector.

The connector on yours is an Aptiv-Delphi Weather Pack connector. The bulletin does not apply to your vehicle/fuel pump.

 

[0xDEADBEEF]

Theoretically, if you crank it long enough to build oil pressure it should fire up, unless your oil pressure sender is bad too.

 

[tayto]

Theoretically, if you crank it long enough to build oil pressure it should fire up, unless your oil pressure sender is bad too.

yes! try unplugging the relay and starting it. seems like an eternity of cranking