Where is the Fuel Pump Relay On GMC SIERRA?

[Mike]

My truck is having some issues turning over and is always dieing then running fine. I'm assuming it's the fuel pump as you cannot hear it turning on anymore, where as before it would turn on, but the truck still had issues running and would always die. I was told to check the fuel pump relay first before i commite to buying the pump.

Where is the relay actually locted? I switched what i believed was the relay located in the fuse panel under the hood. It was labelled like Fuel Pmp and had 4 contacts going into the panel. I swapped it with another one that had all the same number and looked excatly the same. (there was 3 maybe 4 of the same littles blocks that looked the same on the panel)

1999 GMC Sierra 4.8 V8 SLE NEW BODY

 

[Molson02536]

That's your fuel pump relay. Start with the simple and replace the fuel filter, if that did not help then check the fuel pump for pressure. You may be weak on fuel pressure . even a couple of lbs low on a cold start will cause a no start.
Double check cold start cranking fuel pressure. If under 63-62 lbs you have problems.
one test is to give it a squirt of carb cleaner not starting fluid. If it starts then you have a fuel pressure problem.
Run the full fuel pressure test and post back pressures.
Here is the guide lines on testing.
Hard to start cold.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak.
Post back fuel pressure readings.

The 75-85 is only a check on the capable full pressure of fuel pump.
If you can not find the rubber return line check full pressure by plugging return line or just or the true full pressure can be taken direct at the end fuel filter.
What are the pressure readings that you have done.
What are your cold start pressure readings?

Good luck