Fuel pump will not prime

1999 GMC SUBURBAN
200,000 MILES • V8 • 4WD
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TYLER WOODS
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  • 2 POSTS
Fuel pump relay checks fine, fuse is good. Engine runs fine if I manually prime the throttle body with a dribble of gas but the pump won't run before the engine starts. My manual doesn't show details of the primping ckt.
Aug 28, 2019 at 1:54 PM
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ASEMASTER6371
  • ✓ASE Certified Mechanic
  • 52,796 POSTS
  • ASE Certified Mechanic
Good afternoon,

The two second prime comes from the PCM. It is sent to the fuel pump through the relay and the module on the left front frame rail.

I attached a wiring diagram of the pump for you to view.

Roy
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Aug 28, 2019 at 2:09 PM
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TYLER WOODS
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So my problem must be between the relay and the PCM (or the PCM itself) since the vehicle runs well once started. Thanks.
Aug 29, 2019 at 7:26 AM
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ASEMASTER6371
  • ✓ASE Certified Mechanic
  • 52,796 POSTS
  • ASE Certified Mechanic
That is correct. My bet is the PCM.

Roy
Aug 29, 2019 at 8:28 AM
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