Fuel pump relay, no power to orange wire on relay?

Tiny
JEFF HERMAN
  • MEMBER
  • 1989 CHEVROLET SUBURBAN
  • 5.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 100,000 MILES
No power to orange wire on relay. Tracing this wire back to the junction block on the firewall side there's continuity through but the wire doesn't appear to connect to the under dash fuse block but rather joins into a loom that heads back, possibly to the ignition switch. Does this wire get its power from the switch? There's power to all the fuses under dash except ecmb, horn, tl/ctsy, instr. LPS. There's also no voltage to the either orange wire labeled batt. In the upper left of the block. This is a crank, no start but if fuel is poured in the TBI it starts right up. Can't hear fuel pump prime and when power is supplied to the short red test wire on the relay the pump doesn't run. Continuity tests through all fusible links and main grounds are clean and tight.
Sunday, September 7th, 2025 AT 6:00 PM

8 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 54,137 POSTS
Hi Jeff, So there is an oil pressure switch that maybe bad or the engine does not oil pressure. Here is the wiring diagram so you can trace the wires and test for power loss. Check out the images (below). Let us know how it goes
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Monday, September 8th, 2025 AT 11:38 AM
Tiny
JEFF HERMAN
  • MEMBER
  • 486 POSTS
I'll start with the pressure switch. Of course one of the distributor cap bolts broke which wouldn't be such a big deal if this wasn't a long distance project, as in 300 miles from home in the UP of Michigan at my cabins. Probably won't get to it until spring now. Dumb place to put the switch under the distributor if you ask me. Might have to lift it out of the way but we'll see. Any tips would be appreciated.
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Monday, September 8th, 2025 AT 5:13 PM
Tiny
KEN L
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  • 54,137 POSTS
Yep, that is in a tough spot for sure, you can remove the wiring connector and jump it to see if it makes any changes.
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Monday, September 8th, 2025 AT 6:09 PM
Tiny
JEFF HERMAN
  • MEMBER
  • 486 POSTS
Three wires to the switch, which ones do I jumper?
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Tuesday, September 9th, 2025 AT 12:09 PM
Tiny
KEN L
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  • 54,137 POSTS
Hmm, according to the wiring diagram there is two? Make sure it is not the oil pressure sender which is different than the switch.
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Tuesday, September 9th, 2025 AT 5:03 PM
Tiny
JEFF HERMAN
  • MEMBER
  • 486 POSTS
Dumb question but where's the switch supposed to be? Limited signal up here to do research.
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Tuesday, September 9th, 2025 AT 6:42 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 54,137 POSTS
It is down by the oil filter, here is the location. Check out the images (below). Let us know how it goes
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Wednesday, September 10th, 2025 AT 9:56 AM

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