1994 GMC Sierra fuel pump relay

Tiny
GASTON57
  • MEMBER
  • 1994 GMC SIERRA
  • V8
  • 4WD
  • AUTOMATIC
  • 285,000 MILES
I have a 6.5 td with an electric lift pump. The pump does not run, I replaced it and still will not run.I checked the fuse and it does not have power with engine running if I put 12v to the fuse the pump will run so it has to be yhe relay or the oil pump switch. Is there a way to test either one?
Saturday, February 14th, 2009 AT 9:08 AM

1 Reply

Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
According to my info, the only fuse I saw was the crank fuse for the control side of the pump relay, once the key returns to the run position, the relay is no longer energized, then the pump should get voltage from the oil pressure switch in the pump circuit. If you want to check voltage for the crank fuse, the key has to be in the crank position. The relay only supplies voltage to the pump during crank then the o/p switch takes over.

If you do testing at the o/p switch, once you crank enough to bring up oil pressure, the orange is hot all the time, the gray goes hot when the switch closes.
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Saturday, February 14th, 2009 AT 10:12 AM

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