fuel pressure test

[98-k1500-z71]

1998 gmc k1500 5.7 v8
replaced the fuel pump because the truck wouldnt start some days until i whacked on the fuel tank. besides the fact that the fuel gauge isnt working everything was fine for about a week. went to start the truck yesterday and she wouldnt stay running for more than a few seconds. bought a fuel pressure tester and got a reading of 44 psi the first time i tested it and a 48 the second time. i ordered a fuel filter. any other ideas? thank you

 

[kennythewelder]

The fuel pressure needs to be 60+ psi on pre start. It sounds like you may have a fuel pump for a throttle body system and not the one for a Vortec, SPI system. Vortec engines need much more fuel pressure than the earlier system. These trucks are sensitive to this. I have a 1997 5.7 L and have found this out the hard way.

 

[98-k1500-z71]

i havent had any problems starting the truck since i got new bolts for the battery terminals. they have been loose since i bought the truck and after taking them out and seeing how stripped they were im thinking i may have not had a good ground. i still need to do another fuel pressure test though. my main concern now is my gas gauge always being on E after i put the new fuel pump assembly in.

 

[kennythewelder]

The gas gauge float is on that same assembly. It sounds like the float is stuck, or maybe a broken wire on the unit, or something like that. If you pull it again, you can move the float by hand and see if there is a difference in the gas gauge reading, but you will need to put a ground wire on the unit once it is removed, and of leave the wiring connected.