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Poppen and Knocking But Still Rocking 6.2 ???

Discussion in '1982-Present GM Diesel' started by doctor4x4, Dec 20, 2003.

  1. doctor4x4

    doctor4x4 1/2 ton status

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    Want some feedback sugestions what would ya all do - recomend i do ???
    but first the secenaro
    well i bought anouther 6.2 3/4 ton 4x4 Burb but this one is a 1982 unfortunatly this one dont run so good
    1st. it sounds like a slight a rod knock
    2nd it has a poppin sound out the exhaust on the passenger side ???
    and low compression on the 4 that i tested 2 on each set of heads so cylinders nu 3 & 5 an 2 & 4
    only like 200# im suprised it runs (oh wait its a chevy no im not ;-)
    any ways on a good note its looks like it has a fresh rebuilt injector pump and
    all brand new glow plugs :-)
     
  2. ZZ4x4

    ZZ4x4 1/2 ton status

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    Everything you describe could be due to bad fuel injector(s). I had a 6.2 that sounded like it had a rod about ready to shoot out the side. After I cracked the fuel lines at each cylinder (one by one) to bleed out any air the knock went away ( for about 10 seconds). I narrowed it down to two cylinders which everytime I cracked the lines saw air bubbles coming out. The bad injectors let the air go back into the fuel lines, bled out the compression and knocked like crazy. Hope it helps.
    jeff
     
  3. elacruze

    elacruze 1/2 ton status

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    My '85 K35 6.2 rattled like you wouldn't believe, it had sat as reserve in a city fleet for two years. It would hardly maintain 45mph on a light grade. An old GM diesel mech told me to put two quarts of ATF in each tank full until it got better, and one quart each fill till it got smooth. What can I say? 2000 miles later it's smooth as can be, and more powerful than I ever expected. The ATF doesn't seem to affect the cold start, either.

    Eric
     
  4. doctor4x4

    doctor4x4 1/2 ton status

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    Hey Thanks Guys
    Epically you ZZ
    i tried loosining the lines today and sure enough i got to the #6 injector and the poping and slight Knocking went away so now just need to find some good injectors
    I ordered some new ones today so ill put em in tomorrow if they get here in the am as promised and if that works then the tranny fluid tretment is next
    so thanks again
    It Really helped
    /forums/images/graemlins/thumb.gif
    R
     
  5. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    [ QUOTE ]
    My '85 K35 6.2 rattled like you wouldn't believe, it had sat as reserve in a city fleet for two years. It would hardly maintain 45mph on a light grade. An old GM diesel mech told me to put two quarts of ATF in each tank full until it got better, and one quart each fill till it got smooth. What can I say? 2000 miles later it's smooth as can be, and more powerful than I ever expected. The ATF doesn't seem to affect the cold start, either.

    Eric

    [/ QUOTE ]
    DO you know what the tranny fluid does to the motor to make it better? I am curious. /forums/images/graemlins/ears.gif
     
  6. joez

    joez 1/2 ton status

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    It is supposed to help clean it out, since it has so much detergent in it. whether it actually works i dont know, but i have been told by a few guys with very high mileage trucks that they swear by it.
     
  7. elacruze

    elacruze 1/2 ton status

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    ATF is very high detergent. When I bought the truck, I drove it to Michigan from NJ. The first 600 miles, I put in Lucas brand injector cleaner. The first tank got 11mpg, the second and third got 13. It still knocked badly. On the first tank with ATF, it got noticeably better with each startup. It seemed like the heat cycles helped-every time it cooled and restarted, it ran better and better. Now I get 15-17mpg. ATF at .99 a quart was much more effective than purpose-made cleaner at $4.99. At that price, it can't hurt to give it a shot.

    Eric
     

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