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What attributes to dieseling?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Mudstud, Feb 7, 2002.

  1. Mudstud

    Mudstud 1/2 ton status

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    I have adjusted the timing and it's right at 4 above tdc. as it calls for in the manual. This is a sb400 bored .030 over. Everything is stock, no big cam etc. It has just started doing it and it's driving me nuts. What should I check?

    Mudstud
    <a target="_blank" href=http://communities.msn.com/OffroadK5s6superliftand33s.msnw?albumlist=2>http://communities.msn.com/OffroadK5s6superliftand33s.msnw?albumlist=2</a>
    76K5 6" with 33s, sb400/350/203parttime/3.73-D44/GM12bolt
     
  2. txbluethunder

    txbluethunder 1/2 ton status

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    possible cheap gas? did you just fill up?

    1986 K5 Blazer
    Stock and changing soon!
     
  3. shawnboy

    shawnboy 1/2 ton status

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    Carbon buildup will do that as well. Get some good gas additive and take it out for a good romp on the hiway. Good luck.
    Shawnboy.

    <font color=red>If you are having too much fun it's probably illegal.</font color=red>
     
  4. kilroy

    kilroy Registered Member

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    Take a look at your Choke ensure it fully opens when warm, check idle mixture and look for vacuum leaks.
     
  5. Danno

    Danno 1/2 ton status

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    Find some stuff called SeaFoam if you can. Does a great job cleaning up carbon build-up in engines.

    1984 K5 Blazer 4x4 Silverado
    6.2L diesel, 700R4, 3.42 gears, 31x10.5" tires
     
  6. BurbinOR

    BurbinOR 3/4 ton status

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    Check -

    1. Idle speed. Too high will cause dieseling
    2. Timing - you have that covered. However, did you set it with the vacuum line removed and plugged? Important point.
    3. Vacuum lines - make sure you have NO vac leaks.
    4. Octane - if you put 87 in it, try 89 or 92 next time. If you had this rebuilt recently, the compression ratio might be higher than you intended (due to a thin head gasket, etc.)

    For a short term 'fix' (*not really a fix*), shut it off in gear so it won't continue to run-on.



    ONE TON</font color=blue> <font color=green>TPI'd</font color=green><font color=red> BEAST<font color=red>
     
  7. Mudstud

    Mudstud 1/2 ton status

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    Ahhh! You jogged my memory. I know I do have a pretty good vacuum leak under one side of the carb. I tightened that sucker down so much and it still sucks around the base of it. I did disconnect and plug the vacuum advance as well as turned the ideal way down. Plus the last couple of fill ups I have been going to this new cheapy gas station that just opened. I guess I need to replace the carb gasket now and stop using that gas station. You guys rock. Thanks for the tips.

    Mudstud
    <a target="_blank" href=http://communities.msn.com/OffroadK5s/6superliftand33s.msnw>http://communities.msn.com/OffroadK5s/6superliftand33s.msnw</a>
    76K5 6" with 33s, sb400/350/203parttime/3.73-D44/GM12bolt
     

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