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No fuel pressure

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by KILLERK5, Jul 18, 2002.

  1. KILLERK5

    KILLERK5 1/2 ton status

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    My 88' Blazer has been dying while driving lately, but it usually starts right back up, but I can't get it to start this time. The check engine light was also coming on and the engine would run really slugish, it was reading a code 42. I was told to replace the knock sensor, but it didn't help. It's not getting any fuel pressure. I took the fuel pump out and connected it to a 12 volt battery and it worked fine. I checked the voltage at the fuel pump and got 12 volts. I replaced the fuel pump, and it still won't start. What else should I look at? It starts with starter fluid, but thats it. I am stuck, any ideas would help. Thanks a whole bunch!!!!!
     
  2. jc71355

    jc71355 1/2 ton status

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    Fuel Filter, Pressure Regulator, or maybe the injectors? Will it contine to run after you start it with fluid or does it just die after the fluid is gone? Hope it helps.

    James
     
  3. nvrenuf

    nvrenuf NONE shall pass! Premium Member

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    Have you ever replaced the fuel filter?
     
  4. Goober

    Goober 1/2 ton status

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    </font><blockquote><font class="small">In reply to:</font><hr />
    I took the fuel pump out and connected it to a 12 volt battery and it worked fine.

    [/ QUOTE ]
    <ul type="square">
    [*]Did you check to see if it would actually pump fuel under pressure? How much pressure can it make?

    [*]Is there fuel getting to the pump? (check for clogged pickup in tank)
    [/list]


    If all else fails you could install GM Part #12496962 ! That part will fix all engine related problems! /forums/images/icons/smirk.gif
     
  5. KILLERK5

    KILLERK5 1/2 ton status

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    After the starter fluid burns the engine dies. There isn't anyhing in the tank to clog the pump, I cleaned it out 3 or 4 months ago. I replaced the fuel filter, not the fuel pump (sorry!)
    Thanks!!
     
  6. sosamantx

    sosamantx 1/2 ton status

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    there should be a fuel pump relay (as well), is there voltage to the fuel pump?? are things properly grounded?? anyway, i'd check to see if there is voltage starting at the fuel pump and go forward? anyway, just my 2 cents worth! /forums/images/icons/wink.gif

    also, are there any fusible links?

    fyi, i just think it would be easier to check voltage from the pump forward, as you might be able to see the wires, vs. the other way!
     
  7. jc71355

    jc71355 1/2 ton status

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    If your getting 12volts at the pump I don't think the problem is electrical. I think the pump is bad. It might be pumping but it's not enough to run the engine.

    James
     
  8. sosamantx

    sosamantx 1/2 ton status

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    DOH, can't read!! /forums/images/icons/frown.gif make sure there is a proper ground. also, it could be flowing (pumping) fuel under no-load, but it might not have the pressure needed?
     
  9. nvrenuf

    nvrenuf NONE shall pass! Premium Member

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    I tend to agree with the majority that the pump is probably the problem but do rule out an electrical problem. Also, when diagnosing the electrical components don't assume that they should have 12 volt, it is entirely possible that they may be designed to operate with LESS than 12 volts. I did a carb'd motor swap on a 91 K5 and actually had a difficult time finding a full 12 volt curcuit under the hood. Things like the injectors had 9 volts instead of 12. Do yourself a favor and buy / locate a good repair manual if this gets involved.
     
  10. KILLERK5

    KILLERK5 1/2 ton status

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    Is there a way to check the fuel pressure without taking the pump out again? I don't want to take the whole gas tank off again unless i know for sure thats what the problem is. The pump works, it may just be weak. I was told by a mechanic that there should be 12 volts back there when the engine is cranking, so the voltage is correct.
    Thanks for all of the ideas and any more that might help!
     
  11. Thunder

    Thunder 3/4 ton status

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    A code 42 is not the knock sensor. Knock sensor usually throws a 43.
    Code 42 is usually the pick up coil, The EST controll, or maby the distributor module.
    If the ECM does not detect any spark signal I think it shuts off the fuel so the engine does not load up with unburned fuel.
    I would check the magenetic pick up coil and the dist module.
     

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