I have a 2001 Sierra with a 5.3l and I was driving to work the other day when all of a sudden it felt like I had no power and the truck was dying. I stepped on the gas and looked down at the gauges, but the oil pressure and RPM's were just dropping. It then would crank over, but has not started since. I got a tow back to the house and they pulled me from the back end and when i got it home it cranked and it started for a second and then died. I suspected the fuel pump, so I changed that out, but nothing. When I did the fuel pump I bled the pressure off of the line from the nipple on the fuel rail, but I have not gotten pressure like what was on there since the fuel pump swap. Before I swapped the pump it gushed out, but since then it has only dribbled. Any help would be greatly appreciated.

 

Do you hear the pump cycle for a few seconds when you turn the key to Run (not crank)? The pump should cycle for a few seconds to pressurize the system. Do you have a fuel pressure gauge?

 

I agree with fuel pump....you need to get a gauge on there to see what its doing. When you turn the key to run but not start, you should see the gauge go to 60ish for a second then slowly start to fall if you dont start.

 

I do not have a fuel pressure gauge, but I can hear the pump cycle for a few seconds. I am not confident that I am getting enough pressure to the rails though. When I depress the nipple on the fuel rail only a little bit of fuel trickles out. When I bled the pressure off to change the pump I had a rag there and it still sprayed out quite a bit. When I wired the new pump, a walbro 255, I wired the black to the + and the gray to the -. Could it be that those need to be reversed?

 

Hey fellas, thank you for all the help! I had wired the Walbro in the same as the old pump, but I decided to switch the black and grey wires just to see what would happen, and it turned over without a problem!