Fuel pump not working, fuse or relay?

Tiny
REEBENU
  • MEMBER
  • 1990 CHEVROLET SILVERADO
  • V8
  • 4WD
  • AUTOMATIC
  • 152,000 MILES
Pulled tank and tested fuel pump by hooking sending unit straight to battery works fine. Will not work when it is plugged into regular wires. Traced wires did not see any breaks or bad spots. Replaced relay and fuel pump fuse. Also the ignition was replaced about 4 months ago. It died a couple of days ago and I checked to see if it was getting fuel but wasnt sprayed starting fluid in th throttle body and it would star but die of course. I also checked the pump before I pulled tank by runnig a wire from battery to the aldl g wire and nothing happened the book said pump was bad. Please help dont know what else to do!
Saturday, August 16th, 2008 AT 4:31 PM

29 Replies

Tiny
JETSA
  • MEMBER
  • 117 POSTS
So no fuel sprays from the injectors when its turning over. Do you hear the electric pump turning for approx. 3 seconds when you turn on the key? Reason I ask is the problem may be fuel pump related or fuel injector related. Trying to isolate your problem. Reading your issue again, it sounds like the pump isnt working, but I would need verification of my initial question. If the pump is not turning on, you could get a test light and find the fuel pump relay which is located on the firewall behind a black plastic cover on the passenger side under the hood. Find the gray wire and backprobe it while someone turns on the key. This wire goes directly to the fuel pump.

Here is a guide to help check the fuse and the relay with the location of the fuse and relay in the diagrams below.

https://www.2carpros.com/articles/how-to-check-a-car-fuse

and

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

Check out the diagrams (Below). Please run this test and get back to us.
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Saturday, August 16th, 2008 AT 11:49 PM
Tiny
REEBENU
  • MEMBER
  • 3 POSTS
There is no power going to fuel pump through harness relay is new could the oil pressure switch be the problem, or maybe even ecm? I was told that it may be a wire from the battery or maybe even the starter is this true? I need to get this thing on the road to soon. Please help
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Sunday, August 17th, 2008 AT 3:22 AM
Tiny
CHEVYBOY
  • MEMBER
  • 2 POSTS
  • 1990 CHEVROLET SILVERADO
  • 170,000 MILES
So I bought a new one and changed it out. Before I bolted my tank back up I turned my truck to the run position and waited till I could hear it. Once I heard it I shut it back off and bolted the tank back in. Then once I tried it again its not workin. Why is this?
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Monday, July 6th, 2020 AT 4:39 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,176 POSTS
Check the wiring near the pump. Check the connectors between wiring harness and pump. Check for bad grounds.
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Monday, July 6th, 2020 AT 4:39 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Check the fuel pump connector-it should come on for 2 secs when the fuel pump relay is activated-if not check the relay-
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Monday, July 6th, 2020 AT 4:39 PM (Merged)
Tiny
KRISE84
  • MEMBER
  • 1 POST
  • 1988 CHEVROLET SILVERADO
  • V8
  • 4WD
  • AUTOMATIC
  • 204,232 MILES
Hi, I was wondering where the fuse, if there is a fuse, for the fuel pump would be located on this vehicle. Could it be a fuseable link? I reclaced the fuel pump relay today because it cost less than ten dollars and that didn't fix anything. I didn't think that was the problem since both parts ohmed basically the same. I know that the fuel pump runs because I hard wired it to find out. My brother replaced it a while back because he thought that it was the problem. He also cut two of the wires that run to the fuel pump and spliced them. He claims that they were bare from rubbing the frame and shorted out. I replaced what he had spliced in with the correct gauge wire and tucked them in their cover to make sure that they can't rub through again. Anyway, because of what he has told me I would guess that the pump was fine all along and that something else, say a fuse, gave out. Anything that you could suggest or tell me would be greatly appreciated. Note: Someone at a local parts store said that it could just have a relay and not a fuse. Is that true? Thanks
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Monday, July 6th, 2020 AT 4:39 PM (Merged)
Tiny
BLUELIGHTNIN6
  • MECHANIC
  • 16,542 POSTS
Check out the fuel pump oil pressure switch, if it fails then fuel pump will not get power. It is found on teh rear of the engine block near the distributor (4.3L, 5.0L & 5.7L) OR on the left side of engine block under the exhaust manifold (7.4L).
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Monday, July 6th, 2020 AT 4:39 PM (Merged)
Tiny
HIJO DE UN REY
  • MEMBER
  • 1 POST
  • 1989 CHEVROLET SILVERADO
  • 5.7L
  • V8
  • 2WD
  • AUTOMATIC
  • 200,000 MILES
Where is located the oil/fuel pressure switch?
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Monday, July 6th, 2020 AT 4:40 PM (Merged)
Tiny
CARADIODOC
  • MECHANIC
  • 34,331 POSTS
If you're referring to the oil pressure sending unit, it will be screwed in next to the oil filter or right above it on the top of the engine where there's an internal oil passage.
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Monday, July 6th, 2020 AT 4:40 PM (Merged)
Tiny
ROCK283
  • MEMBER
  • 1 POST
  • 1986 CHEVROLET SILVERADO
  • 147,000 MILES
Hi, I have a 1986 gmc 4x4 fuel injected 305 I have spark and the fuses are all good it has two tanks it will not pump fuel and it has 147k on it I know right low k but it sat four 5 years I am 44 and I have bin doing cars since I was 14 and ya I don't know, the pump fuel and its bin siting for 5 years and someone stole the alternator I put a new one on can a guy hot wire the fuel pump to see if works, please help.
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Monday, July 6th, 2020 AT 4:40 PM (Merged)
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,796 POSTS
Yes. You can bypass the relay or remove the cover of the relay and connect the points. It should fire up. After 5 years, it may be good maintenance to replace it.

Roy
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Monday, July 6th, 2020 AT 4:40 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
You can apply power to the fuel pump test connector
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Monday, July 6th, 2020 AT 4:40 PM (Merged)
Tiny
2CP-ARCHIVES
  • MEMBER
  • 4,540 POSTS
  • 1989 CHEVROLET SILVERADO
  • 127,000 MILES
Driving down the road it started sputtering then died. Fuel pump relay good. Fuel pump runs when jumpered. Fuses are good. Something is not letting fuel pump to run. Is it the oil pressure switch? Can it be reset?
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Monday, July 6th, 2020 AT 4:40 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Turn the key On-Do you hear the fuel pump come On? If so check the fuel pressure if its within specs and then comeback with the readings-we start here-
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Monday, July 6th, 2020 AT 4:40 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
If the fuel pump relay is good then check the computer controlled of the fuel pump relay circuit, computer might not be grounding the relay if the fuel pump is not being activated-the oil pressure switch powers the pump after the engine starts
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Monday, July 6th, 2020 AT 4:40 PM (Merged)
Tiny
CHEVYBOY
  • MEMBER
  • 2 POSTS
  • 1990 CHEVROLET SILVERADO
  • 17,000 MILES
Hello I replaced my fuel pump and it works, but im still not getting fuel to my motor. Could it be that my fuel filter is clogged?
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Monday, July 6th, 2020 AT 4:40 PM (Merged)
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
It could be, normally when you replace a pump you do the filter at the same time. The wires in the tank to the pump are very fragile and they may be broken too, if you get the filter off, turn the key on for a brief second an dput the fuel in a jar if it comes out.
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Monday, July 6th, 2020 AT 4:41 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Check the fuel pressure if its within specs and check the injector/s if its opening and closing
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Monday, July 6th, 2020 AT 4:41 PM (Merged)
Tiny
CHUY775
  • MEMBER
  • 1 POST
  • 1990 CHEVROLET SILVERADO
  • V8
  • 4WD
  • AUTOMATIC
  • 175,000 MILES
My 1990 chevy k2500 wont start. Like its not getting fuel replaced the fuel pump but still nothing. Could it be one of the 2 injectors?
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Monday, July 6th, 2020 AT 4:41 PM (Merged)
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
Can you see an injector spary pattern, engine cranking? Use a gage and check fuel pressure. Did you check for voltage and ground at the fuel pump connector, engine cranking?
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Monday, July 6th, 2020 AT 4:41 PM (Merged)

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