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Fuel pump relay wiring...... did a search

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by themaddhatter, Jun 3, 2003.

  1. themaddhatter

    themaddhatter Registered Member

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    Here's the problem:

    Over a month ago, my 91 burban 3/4 ton died. Driving along, and just died in the middle of the road. This being in the middle of the day, I had it towed to a shop, who promptly informed me it was the fuel pump. And when they quoted me $500 /forums/images/graemlins/eek.gif to do it, I said "thanks but no thanks", and had it towed home.

    So, I replaced the pump, and it would run kinda in the yard. Would take forever to start cranking and cranking and cranking. Now, I also went through the ignition system at the same time (distributor was TOAST) and replaced the distributor, coil, oil pressure switch, plugs, wires, cap, and rotor. Still doesn't run.

    Have had this thing only since March. Am getting tired of having a lawn ornament.

    Now, back to why I am here (sorry about biatchin).

    What is the wiring configuration on the fuel pump relay circuit? Where does this get power from? Is it a fused source? I don't hear the pump running anymore. Is there a way to check this out and see if it is a wiring or a relay issue? Can the oil pressure switch be bypassed?

    I want to make this thing work. I bought it specifically for hauling wedding crap to my wedding (it is on the 28th of June), and my fiance is pissed! I work 12 hour days, so I can't spend a hell of a lot of time getting this going now (crunch time).

    Help me out here guys

    themaddhatter
     
  2. BigBurban350

    BigBurban350 1/2 ton status

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    You can usually hear the pump turn on for like 3 seconds when you key the ignition on(not start). Put your head next the the gas tank and have some trust worthy person to turn the key on. If it does turn on, maybe its your fuel filter if you didnt already replace it. If its clogged, it can cause major problems. Good luck.
     
  3. rick88blaze

    rick88blaze 1/2 ton status

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    did you replace the relay itself? i had the same problem last month. i changed the relay and it fixed the problem.
     
  4. themaddhatter

    themaddhatter Registered Member

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    Maybe I should rephrase this whole thing (after almost 30 views and not what I am looking for):

    <font color="blue"> I am looking for information on the wiring configuration of the fuel pump relay. That is what I need.
    </font>
    I know that you are supposed to hear it run for like 3 sec., and that is done by the distributor, etc, etc, etc. If I know the wiring config, I can troubleshoot it some more (start by checking the plug, then go from there).

    Anyone have the wiring diagrams of a 1991 suburban TBI?

    I would REALLLY love to have em

    Could email me at themadhatter@umit.maine.edu

    Thank you
     
  5. HarryH3

    HarryH3 1 ton status Author

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    When the key is switched on, the ECM provideds a ground for the fuel pump relay, turning the pump on for 2 seconds. This brings pressure up in the line. Any time that the ECM detects that the engine is running (via pulses from the distrbutor) it keeps the signal on to keep the fuel pump relay engaged.

    As a failsafe, there is also an oil pressure switch that closes at 3-5 PSI and provides a 2nd circuit for the fuel pump. So if the relay fails, then the pump will still kick on after the engine spins over and starts to build oil pressure.

    First thing to check is to see if there is power at the pump itself. The main power feed to the pump is fused, but I can't recall right now where the fuse is located. (Haven't had my coffee yet!) /forums/images/graemlins/blush.gif
     
  6. themaddhatter

    themaddhatter Registered Member

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    Hey Harry,

    Yeah, what is going on is the pump does NOT turn on at the initial key on, nor does it when the distributor rotates.

    Seeing as I just replaced the pump, distributor, and the oil pressure switch, I am now trying to discern the power situation.

    Any relay works by taking a low amp line to turn on a high amp line. I am trying to find out where that high amp line is getting it's feed from. It has been raining here for a week, and I am not going to crawl around in the mud trying to troubleshoot this.

    If anyone has a wiring diagram for a 1991 TBI Chevy (ANY CHEVY) let me know.

    And if anyone knows where the magical power lead is from, that would ROCK!!!! /forums/images/graemlins/thumb.gif

    themaddhatter
     
  7. themaddhatter

    themaddhatter Registered Member

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    Anyone?

    It is Friday, and the weekend will soon be here.

    ANYONE?

    Just looking for a TBI wiring diagram for a 91 burban here folks, not the ark of the covenant......
     
  8. K5 NUTT

    K5 NUTT 1/2 ton status

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    Location:
    Grand Junction Colorado
    Red wire...test lead - circuit 490
    Tan/White...output to pump 120
    orange...Ign power from ecm 1 fuse 440
    blk/white...ground 450
    drk grn/wht...to ecm connector cav a1 controls relay 465

    all realys can be bypassed by jumping terminal 30 (power) to 87/87a depending on how the relay is wired...in this case jump the tan/wht wire to the orange wire...

    DW
     

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