2000 GMC C1500 Fuel Pump and Electrical

Tiny
HARRISON1
  • MEMBER
  • 2000 GMC C1500
  • V8
  • 2WD
  • AUTOMATIC
  • 145,000 MILES
Changed my fuel pump last year thinking it was causing my truck to miss intermittently. Bought a Delphi pump. Has been working great up until a few weeks ago. Tried to leave my work, and no start. Towed to dealer and truck started. They checked everything and stated they could not find anything wrong. I picked up truck drove home and again the truck would not start. Has 0 fuel pressure when this happens. I can let it sit sometimes and cycle the key on and off then the pump will come on and it starts and runs fine. The pump seems to not want to "start-up" after its warm. Once the truck is running it will stay running. Only when I turn off the truck does this happen. It happens intermittently and you don't know when. Where do I start? Have check all fuses and swapped relays, replaced oil sending unit, buffed and cleaned all ground wires.
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Sunday, September 12th, 2010 AT 8:40 AM

10 Replies

Tiny
WRENCHTECH
  • EXPERT
You simply start by verifying power and ground arriving at the pump when the problem is present. Double check that all the contacts are tight in the harness plugs because they are known to have a problem with that. If all that is eliminated, replace the pump.
Try not to ever let the fuel go below 1/4 tank because that ruins the pumps.
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Sunday, September 12th, 2010 AT 8:55 AM
Tiny
HARRISON1
  • MEMBER
Easier said than done. Always happens when I am away from home and tools. Only twice has this happened at home. How do I get to the tank wires on top of the tank without dropping it or removing the bed?
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Tuesday, September 14th, 2010 AT 7:05 AM
Tiny
WRENCHTECH
  • EXPERT
The harness has a plug where it enters the tank if you crawl underneath.

I know intermittents are very hard to deal with. We have to do it all the time but there is no other way without just throwing parts at it which can get very expensive and fix nothing.
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Tuesday, September 14th, 2010 AT 7:12 AM
Tiny
HARRISON1
  • MEMBER
Do you have a wiring diagram of the fuel system you could share for this model?
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+1
Tuesday, September 14th, 2010 AT 7:12 AM
Tiny
HARRISON1
  • MEMBER
I know the harnesses well. Had to rewire one when I replaced the pump (square to flat oval). Does your arm fit up over the tank to unplug the harness? I spent a lot of time under there when I dropped the tank last time, I had to plug those two harnesses into the pump before I raised the tank up. Very little room and you work blind. --- I do know about the prime test port in the fuse box under the hood. All Good. System holds pressure. Will start sometimes, with leftover pressure then die. I thought since it worked for a year maybe my rewire job may have gone south. But that should be consistent. I went outside to duplicate problem yesterday, started everytime (5 trys at various intervals even after I let it run a while) and no luck.
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Tuesday, September 14th, 2010 AT 7:28 AM
Tiny
HARRISON1
  • MEMBER
Well, not enough room to get my arm in to pull the harnesses. I pulled the bed. All connections looked good but the ground wire (black) where I connected them had gotton hot and the plastic sleeve was baked until it was crispy. Cut the entire thing off again. Stripped and soldered the ends together this time instead of using those straight connectors that come with the pump and the rewire. Wrapping up very well each wire and then the bundle and back into the loom. Plugged in the pump again and it started again. It started all morning with no intermittents. I let it get hot but could not generate a failure. I even drove it around a while. I ordered another new pump (Delphi) FG0053 and will install that. Why? Well when I was running it the final time with the bed off I heard a strange noise that was coming from the pump. I had the truck running about 2 minutes and all of the sudden the pump started a funky noise. Not the same when it is just running. It sounded like a bearing was seizing up in the thing and was giving a loud squeeking sound. Then it stopped. Motor running the entire time. Could be overheating and cutting out for whatever reason. Another weird thing when this started is I drove from Dallas to College Station to take Daughter back to College and then back and it never quit on me. I was too scared to cut it off when I refuled in Waco. But she made it. I will let you know if the new pump does it.
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Tuesday, September 14th, 2010 AT 7:46 PM
Tiny
HARRISON1
  • MEMBER
I replaced pump. Been driving 6 months and all is well. I added a test wire from the pump voltage feed to the side of the frame to allow me to test easily if I am getting 12 volts to the pump from now on. Used a 16 guage wire soldered in harness, wrapped, sleeved, capped, and stowed so no chafing or corrosion can happen and short out. Thanks for the help. Anyone have a Bed Lift out yet instead of using 5 friends to lift up and place the bed on the truck frame? That is the way to go. Its so much easier to work the pump that way. 6 Bed bolts, all wiring plugs in one spot, and disconnect the fuel fill at the bed. Comes right off.
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Saturday, February 26th, 2011 AT 4:06 PM
Tiny
WRENCHTECH
  • EXPERT
I do them alone by removing the left side bolts and leaving the right side loose. Then I use a pole jack at the fender well to tilt the bed sufficiently to access the pump. Just be sure to use safety blocks to prevent the bed from falling on you.
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Saturday, February 26th, 2011 AT 4:09 PM
Tiny
HARRISON1
  • MEMBER
I will try this next time (hope I don't have to) if it gives me more trouble. I did sorta try this but I was afraid the bed was gonna slide off the right side. I didn't leave any bolts in the bed loosened up. Thanks for the help on this and all the replies !
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Saturday, February 26th, 2011 AT 4:19 PM
Tiny
WRENCHTECH
  • EXPERT
Just closing out the question
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Friday, March 11th, 2011 AT 4:23 PM

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