Fuel pump relay?

Tiny
ANONYMOUS
  • MEMBER
  • 2002 GMC C1500
  • 240,000 MILES
I thought that my fuel pump went out but after removing the bed I discovered that I do not have power at the plug fior the fuel pump. I checked all connections and they are fine. I only have power on one leg of the relay. The relay has been changed so it should be good, fuses are good. So what do I check to figure out why I have no power across the relay and at the plug for the pump?
Sunday, November 11th, 2012 AT 8:54 PM

20 Replies

Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
At the intial prime, key on, no crank, can you hear the pump run for a few seconds? The fuel pump relay has two separate voltage sources. One voltage source for the load side of relay, terminal 30 hot all the time. The other voltage source is for the coil side of relay, green wire with white tracer, voltage comes from pcm. During initial prime only hot for a few seconds. Engine cranking should be all the time if rpm signal is present. Could be issue with wiring circuit--wiring connector or other. Any applicable trouble codes?

I looked at gmc sierra 1500 4.3L
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Sunday, November 11th, 2012 AT 9:08 PM
Tiny
POEMAN
  • MEMBER
  • 2 POSTS
  • 2000 GMC C1500
  • V8
  • 4WD
  • AUTOMATIC
  • 230,000 MILES
2000 GMC 1500. Where is the fuel pump relay. Here is what has gone down to date - truck started and then died after running out of fuel. I placed 4 gallons of fuel in the tank and cannot get truck to start. Have replaced fuses to fuel pump and relay under the hood. Does anyone have any ideas for me?
Thank you
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Wednesday, February 3rd, 2021 AT 1:26 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Hi poeman, Welcome to 2carpros and TY for the donation and selecting us as your auto repair site Feel free to ask questions at anytime and Merry Christmas and a Happy New Year 2010

Do you hear the fuel pump come on? If so do below

Do a fuel pressure check to rule out a clogged fuel filter, intank pick-up sock and a burned-up fuel pump. Also check for injection pulses
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Wednesday, February 3rd, 2021 AT 1:26 PM (Merged)
Tiny
POEMAN
  • MEMBER
  • 2 POSTS
Thank you for response and Merry Christmas to you as well. I did not here fuel pump kick on.
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Wednesday, February 3rd, 2021 AT 1:26 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Check the ECM B fuse 20amp in the underhood junction block. If okay test or swap the FP Relay in the same location. If both okay.

Do this direct battery positive voltage to the fuel pump connector gray wire and negative post to the black wire -Did the fuel pump come On? If the fuel pump don't come on and the ground side of the pump is good=Replace the fuel pump-Good Luck


https://www.2carpros.com/forum/automotive_pictures/12900_fp1_20.jpg

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Wednesday, February 3rd, 2021 AT 1:26 PM (Merged)
Tiny
SMITH450
  • MEMBER
  • 1 POST
  • 1996 GMC C1500
  • V8
  • 2WD
  • AUTOMATIC
  • 240,500 MILES
Previously ask question, I have no elect. Poser to my fuel pump. I replaced the fuel pump and fuel pump relay. I have a Haynes repair manual and the Elect. Diagram only shows the fuel pump relay, is there another fuse and where would it be located.
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-1
Wednesday, February 3rd, 2021 AT 1:26 PM (Merged)
Tiny
BLUELIGHTNIN6
  • MECHANIC
  • 16,542 POSTS
Fuel pump fuse is called ECM B, fuse number G12-F11, 20Amp fuse, located in the underhood fuse/relay center ( circled below).


https://www.2carpros.com/forum/automotive_pictures/261618_Noname_490.jpg



Thanks for using 2CarPros.com!
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Wednesday, February 3rd, 2021 AT 1:26 PM (Merged)
Tiny
MITCH2020
  • MEMBER
  • 3 POSTS
  • 1991 GMC C1500
  • 5.7L
  • V8
  • 2WD
  • AUTOMATIC
  • 160,000 MILES
It will start run a min. Or so than shut off, watching it the fuel stops coming in, we have changed the fuel pump and the fuel relay still doing the same thing.
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Wednesday, February 3rd, 2021 AT 1:26 PM (Merged)
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Unplug map sensor if it runs relace the sensor also check vacuum hose if soft replace that due to it sucking together and causing map sensor to make like it fails. Check pcv hose as well if soft replace that.
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Wednesday, February 3rd, 2021 AT 1:26 PM (Merged)
Tiny
MITCH2020
  • MEMBER
  • 3 POSTS
Un plugged map sensor still did not run ck hose it looked fine, changed hose and pcv valve no change. When it did start for a min. It backed fired real bad than died. Any ideas
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Wednesday, February 3rd, 2021 AT 1:26 PM (Merged)
Tiny
MITCH2020
  • MEMBER
  • 3 POSTS
Also every time it stops running you can here the fuel pump running and then it stops running after a few sec.
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Wednesday, February 3rd, 2021 AT 1:26 PM (Merged)
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
The fuel pump is normal. Do basic engine checks and test ignition module and pick up coil check for bare wires on pick up coil. Should have about 600-800 ohms resistance on pick up. Other than that scan for codes.
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Wednesday, February 3rd, 2021 AT 1:26 PM (Merged)
Tiny
KRISWASELICH
  • MEMBER
  • 2 POSTS
  • 1990 GMC C1500
I was driving on the beach one day and the truck cut out and off. Through process of elimination I found that it was a fuel problem. First I checked the lines and found some kinks and a crack but no leaks and didnt hear my pump running. I had to buy a new gas tank when I went to install my fuel pump because of rust. The lines from the sending unit actually broke off when I dropped the tank because they were rusted so bad. I of course installed a new sending unit also. I found that my fuel pump fuse was blown so I changed it. One of the guys with me when it happened decided to cross my wires before the fuse to do a "smoke test" and then shorted something deeper in the system. I created a temporary alt. Hot to the pump to isolate where my problem was and the pump would run and the car would try to start. I sounds like its not getting enough fuel pressure at the TBI and when I watch it come out of the injecters it doesn't seem to spray the way it should. None of the lines leak, and when I bypass the relay the fuse doesnt blow. What does the relay do and if it is bad would that be the reason my pressure is deficient? Is there a certain hot that pressurizes at the injector plugs on the TBI? Does it make a difference if the injector plugs are switched?
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Wednesday, February 3rd, 2021 AT 1:26 PM (Merged)
Tiny
LOSONE
  • MECHANIC
  • 1,616 POSTS
The fuel pump relay acts as fuel primer for between 3 and 9 seconds. The circuit is completed through the oil pressure switch when oil pressure comes up. If you are direct wired and the pump doesn't function replace the pump without question. Let me know here is the relay location and the wiring diagrams in the diagrams below.

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

Check out the diagrams (Below). Please let us know what happens.
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Wednesday, February 3rd, 2021 AT 1:26 PM (Merged)
Tiny
KRISWASELICH
  • MEMBER
  • 2 POSTS
I already changed the fuel pump and I found a good fuel relay off a junk suburban and now the fuel pump spins constantly, no fuses blow, but the TBI is not getting any fuel. I tried turning the key on and off to let the pump run but it doesn't even seem to fire a little. It cranks over at a normal speed. I had to change the top of my TBI because when I changed the lines I cross thread and stripped the holes in the back. I changed the gaskets and cleaned out the injectors real good with kerosene. Before this fuse problem it was spraying strong. Yesterday before putting in the new fuel relay it still flowed from the injectors but with less pressure. Now today nothing. Where is my oil pressure switch and does it matter if I have an oil leak?
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Wednesday, February 3rd, 2021 AT 1:26 PM (Merged)
Tiny
LOSONE
  • MECHANIC
  • 1,616 POSTS
The presure regulator is in the throttle body. It is the hump on top. Parts stores sell a rebuild kit that is not expensive. On the other hand the used pump might be bad or some trash in your filter. If I was there I could put my hand on the problem. I have fixed hundreds. Good luck
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Wednesday, February 3rd, 2021 AT 1:26 PM (Merged)
Tiny
TJONES65
  • MEMBER
  • 1 POST
  • 1990 GMC C1500
  • V8
  • 2WD
  • AUTOMATIC
1990 gmc truck would not bust over when it got cold in the mornings but it would start up when it seemed warmer. One day when I got home from work I tried it and it did not start I put gas in it because it was low on gas and I started it and it ran. So I took and filled it up and the next morning it was cold and it didnt start up and has not since. I checked and it is getting fire to plugs, so I checked for fuel before the fuel filter and it was not getting fuel. Make the story short I ended up changing the fuel pump relay, fuel pump fuse, and fuel pump and still can not get any fuel, what could be the problem?
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Wednesday, February 3rd, 2021 AT 1:26 PM (Merged)
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
Check the fuel pump inline fuse. Passenger side firewall. Picture below.
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Wednesday, February 3rd, 2021 AT 1:26 PM (Merged)
Tiny
MARKE182
  • MEMBER
  • 1 POST
  • 1988 GMC C1500
  • V8
  • 2WD
  • AUTOMATIC
  • 220,000 MILES
Where is the fuel pump relay located?
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Wednesday, February 3rd, 2021 AT 1:27 PM (Merged)
Tiny
JERRYGOODWRENCH
  • MECHANIC
  • 77 POSTS
Usually on the firewall unmarked. You might need to findsomeone with a component locator book or try the library.I usually have to trace the wiring from the fuel pump to the eng compartment. Whats the problem?Fuel pump not running? Let me know
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Wednesday, February 3rd, 2021 AT 1:27 PM (Merged)

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