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No power to the fuel pump?

Discussion in 'The Garage' started by ryan91k5, Dec 13, 2005.

  1. ryan91k5

    ryan91k5 Registered Member

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    I have a 91 k5 with a 350 and TBI fuel injection. The other day the engine stalled while driving, but I was able to pop it in N and fire it back up right away. It being cold up here (Manitoba) I added some gas line antifreeze in case there was some moisture in the tank. Well it happened a couple more times but had seemed to go away for a day or so.

    Well today the motor died completly and won't fire back up at all now. Figured maybe the filter got all gummed up so pulled the tank end of the line going into the filter and cranked over the motor and to my surprise, no gas came out. Well, then I figured maybe the pump is shot. Well I happened to have the rear carpet out and the previous owner had cut an opening out above the pump. (doesn't look like he replaced it though). So I had a look at the pump and sure enough with the key on or cranking the pump doesn't turn on. Well just to be sure before pulling the pump, I wanted to make sure it was getting power so I unplugged the connecter at the front of the tank (2 wires, 1 power and one for sensor? these wires lead to the pump, there is one other one at the pump hooked to ground) and connected my multimeter up with the key on and neither wire is getting any voltage.

    So now my question is, where do I look next? I don't have any diagrams of the wiring harness so I'm kind of lost here. I was going to hook a +12 up to one of the 2 wires to make sure the pump works but didn't want to fry the sensor wire if I guessed wrong :)

    Ryan
     
  2. B_to_C

    B_to_C 1/2 ton status Author

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    I had the same problem on my 90k5. After spending $$$ on a new sending unit / pump and taking a week to install it, I found out that the power wire had corroded inside the plastic sheathing -so you couldn't see it was corroded. Good luck!
     
  3. ryan91k5

    ryan91k5 Registered Member

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    I guess I could trace the wire back to the harness and check it for conductivity. I hate working on my truck in winter :)

    And yeah I figured for sure the pump was gone, but thought I might aswell run a quick voltage check and sure enough the pump isn't getting any power....

    Ryan
     
  4. chevyjeff

    chevyjeff 1/2 ton status

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    hook your test light or volt meter up to the green wire (i think) do this at connector under truck by the shock mount on frame. lay volt meter on tire so you can see it then turn key on you should get 10-12 volts for 1-2 seconds. the pump wont get cont. power until truck gets oil psi. if you dont get power i would bet its the fuel pump relay.
     
  5. ryan91k5

    ryan91k5 Registered Member

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    yeah I had my test light jammed in the connector, the light never came on and I verified the ground I was using with different +12 source. So it looks like the wire isn't getting power for sure. I was doing some searching and it sounds like the fuel pump is connected to the ecm b fure in the block. I'll check that when I get home, but a blown fuse wouldn't explain the intermittant stalling I had a couple of days ago.....

    Is the relay mounted on the firewall I assume?

    Ryan
     
  6. mouse

    mouse 1/2 ton status

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    Double check the power at the pump. It should only get the 12 volt signal for 1 second and then shut off. The fuelpump relay is mounted on your firewall. It should be on the passenger side, if its like my '89 suburban. There is also a fuse for that circuit so check for that as well. It seems like it could be a clogged tank screen, so I would try to eliminate any problems with the circuit first.
     
  7. nemesis_pyros

    nemesis_pyros 1/2 ton status

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    Hey another guy from winnipeg, we gotta get together and do some wheeling some time. I'd recomend what the other guys mentioned and also get a Hayes manual for your truck from Canadian Tire or Princess auto. Its the best tool you'll ever get. If you still can't figure it out drop me a line and maybe we can set something up and I'll take a look at it.

    Brent
     
  8. 89GMCSuburban

    89GMCSuburban 1/2 ton status

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    Test your ignition module, if it craps out, the ECM will not turn the fuel pump on...so if that's the case, you wouldn't be getting any power at the fuel pump. Happened to mine...
     
  9. driney

    driney 1/2 ton status Premium Member

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    Up by the relay on the passenger side firewall, their should be a wire hanging down with a female spade connector(I think). If you apply 12 volts fused to it , your fuel pump should have power. Maybe a quick way to check out your harness.
     
  10. ryan91k5

    ryan91k5 Registered Member

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    thanks for all the help guys! I double checked the power at the point where the tank harness connects to the 2 wires from the relay. Now that I know it only gets +12 for the first couple of seconds, sure enough it was getting power.

    So I figured then the pump was gone. Go buy a new pump and filter (~$100 canadian). While handling the pump/sending unit assembly, I noticed one of the wires at the connecter on the top didn't look so good. Upon closer inspection, sure enough the only part left connecting the wire was the jacket, the rest had opened up and corroded into the wire and I guess finally broke connection. And this connector is the wires molded in kind, not the servicable kind.

    So I goto the local parts store to find the connector on top of the pump assembly and they tellme the wire harness on the outside of the pump assembly (+12,ground and gas guage) only comes with the sender unit and Chevy would want around 300 for it! Well I wasn't about to spend 3 bills on for a connector, and didn't feel like running accross town to the wrecker in the snow. So I just melted away the plastic around the terminal enough to get a decent solder joint, then just epoxied er all up.

    Pretty bush fix, but I've tied off the wires to alleviate any stress on the solder joint and it should hold till the summer anyways. So in the end, I replaced a perfectly good pump, but with 300k+ who knows when the last time it was replaced anyays.

    Thanks for all the help guys!
     
  11. B_to_C

    B_to_C 1/2 ton status Author

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    :woot: I think that's the first time my advice has been correct :haha:
     

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