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Fuel pump will not prime

Tiny
TYLER WOODS
  • MEMBER
  • 1999 GMC SUBURBAN
  • V8
  • 4WD
  • 200,000 MILES
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.
Wednesday, August 28th, 2019 AT 1:54 PM

3 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
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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Wednesday, August 28th, 2019 AT 2:09 PM
Tiny
TYLER WOODS
  • MEMBER
  • 2 POSTS
So my problem must be between the relay and the PCM (or the PCM itself) since the vehicle runs well once started. Thanks.
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Thursday, August 29th, 2019 AT 7:26 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
That is correct. My bet is the PCM.

Roy
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Thursday, August 29th, 2019 AT 8:28 AM

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