1998 Sierra Mystery :(

[bsowi967]

Hello! I have a 1998 GMC sierra. 5.7 vortec. Ran perfect for 5 months. Shut it off when i got to work 2 weeks ago, end of the day rolled around and it wouldn't start. Turns over but wont fire. I have spark, replaced fuel filter, and replaced fuel pressure regulator. Perfect fuel pressure all the way up to the injectors. Narrowed it down to no injector pulse. I replaced the cam sensor and nothing different happened... but when i tested it, i dont think it was getting any power. Any ideas/ suggestions?? I just don't get what could've happened in 12 hours that it went from perfect to nothing. I was also looking into possibly the calpac failing on the ecu causing it to go into limp mode. is this possible also?? Thank you so much again! any ideas/ suggestions are more than welcome!!

Thank you,

Brandon

 

[Rags]

Try Unplugging the Throttle position sensor .. i have had 1 go bad and show the computer wide open throttle which will shut off the injectors. That was fun to figure out so just give it a try before you go to much further with random parts. if its bad it should start unplugged.

 

[bsowi967]

Thank you! I'll try that tomorrow!

 

[Rags]

Also check to see if your check engine light comes on at key on engine off! .. if not , there is no comunication with the computer, if thats the case check your ECU relay. just swap it with a different relay that is the same, just not the fuel pump relay

 

[Molson02536]

Hello! I have a 1998 GMC sierra. 5.7 vortec. Ran perfect for 5 months. Shut it off when i got to work 2 weeks ago, end of the day rolled around and it wouldn't start. Turns over but wont fire. I have spark, replaced fuel filter, and replaced fuel pressure regulator. Perfect fuel pressure all the way up to the injectors. Narrowed it down to no injector pulse. I replaced the cam sensor and nothing different happened... but when i tested it, i dont think it was getting any power. Any ideas/ suggestions?? I just don't get what could've happened in 12 hours that it went from perfect to nothing. I was also looking into possibly the calpac failing on the ecu causing it to go into limp mode. is this possible also?? Thank you so much again! any ideas/ suggestions are more than welcome!!

Thank you,

Brandon

Start with the simple and check all your fuses and also have the ICM checked to make sure it has not gone bad.

Start with these simple things and was can go from there.

Good luck and hope you get your Sierra running again soon.

Molson02536