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

[George B]

I am thinking you might have a damaged wire or poor connection. You may be able to read voltage with a meter but the circuit doesn’t seem to be able to carry the current needed to run the pump.

 

[rockola1971]

Sounds like fuel pump wiring harness/plug (Vehicle side NOT fuel fump side) needs replaced. Its a fairly normal procedure to need to replace the vehicle plug side for fuel pump since it is passing power every second the vehicle is running....for years and years. They tend to overheat and get melted. Especially if the fuel pump shorts and melts and draws an excessive amount of current until it is dead.

It is not at all uncommon to read voltage at a terminal of a connector but it wont pass any power because of a very high voltage dropped caused by burnt/carboned up terminals.

 

[jj3393]

We replaced that harness (female). Think the ground is bad and trying to determine where to re run a ground for it

 

[Fless]

One other thing you could check is the PCM connectors (under the hood, driver side near the front). They can get water in them and it can hamper the connections. Pull both connectors and check for water migration, corrosion, and a good connection, especially in the lower part of the connectors.

If you can connect a couple of bulbs (for a good amp load) to the pump 12v connector feed, you could see if they light brightly or peter out when the ignition is on.

 

[Coveman]

Do these vehicles have the low-oil pressure fuel cutoff switches? That would interrupt the power supply.

 

[SnowDrifter]

Do these vehicles have the low-oil pressure fuel cutoff switches? That would interrupt the power supply.

nope, just a float in the pan for oil level

To confirm things with OP:

Fuel pump has power and ground, however there's a voltage drop when the fuel pump turns on, and the unit fails to function?

 

[swathdiver]

ECM?

 

[V327839]

Yes they do have an oil pressure cutoff. I had a similar issue with my 01 Yukon then with 04 sub after engine swap. If the oil pressure sender at the back of the block behind the intake reads fully open, it will interrupt fuel. Crank all you want, no start and no codes. Try replacing that switch if possible.

 

[Fless]

Hopefully @jj3393 will come back and let us know if there was a solution.

 

[rockola1971]

Yes they do have an oil pressure cutoff. I had a similar issue with my 01 Yukon then with 04 sub after engine swap. If the oil pressure sender at the back of the block behind the intake reads fully open, it will interrupt fuel. Crank all you want, no start and no codes. Try replacing that switch if possible.

Thats very odd. Using a 2002 schematic there is no oil pressure switch in series with the fuel pump or the fuel pump relay. I havent seen a GM vehicle use that configuration for around 30yrs.