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Bad Fuel Pump??

Discussion in '1969-1972 K5 Blazer | Truck | Suburban' started by ErikH, Sep 27, 2001.

  1. ErikH

    ErikH 1/2 ton status

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    HELP! My bad idle situation continues unchanged, and I've replaced everything but the carb and fuel pump... Dammit!

    So, does anyone know if a bad fuel pump, in additional to causing a crappy idle, would cause my truck to backfire during gear-shifts and engine-braking? It seams that backfires would be the result of a vacuum leak, bad timing, or a worn carb, not a faulty pump...

    My carb is barely 6 months old and I just thoroughly cleaned it. I just replaced the intake gaskets, and I did so very carefully according to Edelbrock's instructions. I just replaced the distributor, coil and plugs, and my electronic ignition is firing strong at 8-degrees BTDC.

    All I have left to replace is the fuel pump and carb. You can imagine what I'm hoping is bad.
     
  2. Burt4x4

    Burt4x4 3/4 ton status

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    Hmmm, well I know a fuel pump can start to loose fule pressure but does that cause backfire? duno?
    Is it backfireing out the carb or your pipes?
    What about you plug wires? I had a set of wires that was giving me all sorts of strange symtoms. I bought a set of 8mm Summit blue wires(Taylor Made) and bam! solved my issues with hessitation and loos of power and some carb backfire. I think the fuel/air wasent getting burned and then the spark was getting there and by then the air/fuel was everywere in the intake and BOOM!!!!
    Hope this helps

    72K5[​IMG]Led Zeppelin[​IMG]Rock ON![​IMG]
    <a target="_blank" href=http://www.geocities.com/baja/5099>www.geocities.com/baja/5099</a>
     
  3. 71RestoRod

    71RestoRod 1/2 ton status

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    Gotta 2nd Steve on checking or replacing the plug wires... particularly if you run w/ headers. I ran into the same trouble many years ago with a basically new set of wires. (nice 8mm wire too). I even took it to a shop and asked them to scope it because I suspected the trouble was with the wires. I was told that the wires checked out fine... but it still ran like crap. After spending more time and money, I finally sprung for (another) new set of wires anyway and... bingo... all better. Since then I've always used insulator sleeves over the spark plug boots to protect the wires from the heat. They seem to fail right at the boot.
     
  4. ErikH

    ErikH 1/2 ton status

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    Hmm... I'm running relatively new (and pricy) 8.8mm MSD plug cables. They're snug and kept well-away from the exhaust manifolds (no headers, yet). I do appreciate the help, but I don't think the wires are in question...

    I'm gonna buy a new Edelbrock Performer carb from Pep Boys and test it on my engine. If it works, then I'll return the carb and buy an Edlebrock Quadrajet from Jegs. If it doesn't make a difference, I'll change the wires. Arg!
     
  5. ErikH

    ErikH 1/2 ton status

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    Oh yeah, to answer your question, the backfires are exhaust-related, not coming from the carb.
     
  6. POFF

    POFF 1/2 ton status

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    You can get backfiring and poping if the timing is off. Points? Check them. Usually if the fuel pump is going out it will effect top-end.

    Never said I could spell!
    '70 K-20 San Diego, CA
     

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