The fuel pump on my GMC Sierra truck was bad. It was replaced and is still...

[Shannon]

...not starting.? The truck is a 1999, and I am absolutely sure it is the fuel pump. Why wouldn't this brand new pump be working?

 

[Molson02536]

...not starting.? The truck is a 1999, and I am absolutely sure it is the fuel pump. Why wouldn't this brand new pump be working?

Have you inspected the wire harness and fuel pump relay?? The ground wire to the sending unit is separate from the rest of the harness and is common for it to corrode off leaving a open circuit to the sending unit causing it not to work.

The other thing you should also check is the fuse to the ECM on your Sierra, the ECM fuse also provide the 12Volts needed for the sending unit and if there was a short from the old pump if it was bad could have blow the fuse to your ECM.

Start with those things to check and post back, good luck