2002 GMC Sierra Fuel pump or sending unit problem

BADMANBRAD

MEMBER
2002 GMC SIERRA

Electrical problem
2002 GMC Sierra 6 cyl Four Wheel Drive Automatic

I have a 2002 GMC Sierra 1500.

The truck had stopped, and it appeared to be the fuel sending unit
That unit is a canister containing the fuel pump as well, and goes for about $400 retail.

To get the truck back on the road temporarily,
We changed the fuel pump (not the whole canister) and "hot wired" the fuel pump to a switched ignition 12v (fused) source.

The first time this was done, it worked fine for 1 week
(the pump burned out).

We bought a new fuel pump and tried again.
This time, its working, but it takes 3-4 cranks before it starts.
It seems that the fuel pressure must be off, but we have no way to verify this.

1) What does the sending unit do?

2) How many volts is the fuel pump?

(i checked the voltage at the sending unit and it was only 5 volts)

Any ideas for a solution?

1 Reply

JDL

MECHANIC
16,098 POSTS

Hello, the factory wiring circuit to the pump, the gray wire at the pump connector should have good voltage, engine cranking. You can take a reading across your battery posts, engine cranking, that may vary from one vehicle to another, maybe 9.5 to 10 volts or better. The reading at your pump, engine cranking should be close to the same reading. Also check ground at the pump connector. If the voltage reading at the pump is too low, go to the relay, check voltage there.

As far as your hot-wired circuit, I can't track that circuit.