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Edel. Q-jet is deseling when shut off??

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Burt4x4, Sep 6, 2000.

  1. Burt4x4

    Burt4x4 3/4 ton status

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    Hello everyone,
    I put 87 octane in my rig the last couple of tank fulls instead of the 92 that I normally run and now when I shut off my rig the motor trys to keep running, deseling,also when a constant RPM 2800 going down the road in 3rd gear I get backfire or pop pop thru the exahust?????
    Any thoughts would be AWSOME!!

    Rock ON![​IMG] 72 K5 [​IMG] Led Zeppelin
    http://burt4x4.coloradok5.com
     
  2. archer

    archer 1/2 ton status

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    Sounds like a little more than lower octaine. maybe time to tune it up and check the timing/idle etc. I went down in octaine and experienced a little more knock under load than usual but none of the other symptoms. Sometimes backfiring can also be indicative of buildup in the carb. Just clean it with carb and choke cleaner. Beyond that you may need some more detailed carb diagnosis and/or adjustments.

    "who dares wins"
     
  3. Shawn

    Shawn 1/2 ton status Premium Member Author

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    You're going to have to keep running 92 or retard your timing. You could also try to clean the carbon deposits by running some ATF through your carb. Your neighbors won't like the smoke when you do this. Not sure why you're getting a backfire at that RPM but the carbon build-up could be related. When you run lower octane, the carbon build up acts like a glow plug (causing dieseling effect).

    Shawn
    87 K5
    few mods
     
  4. realsquash

    realsquash 1/2 ton status

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  5. Burt4x4

    Burt4x4 3/4 ton status

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    I have the stock fuel pump. I am running at 10deg timming.The motor is 350 board 30 over w/ flat top pistons
    also running MSD 8360 dist. going to put on a 6A box this weekend. Oh ya the 194 - 150 valves too.....
    The carb is about 3 1/2 yrs old I should tare it down and clean it eh????
    Thanks

    Rock ON![​IMG] 72 K5 [​IMG] Led Zeppelin
    http://burt4x4.coloradok5.com
     
  6. sosamantx

    sosamantx 1/2 ton status

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    <font color=blue>It still sounds like too much timing for the lower octane. I believe 8 degrees is stock, and I normally set my timing between 8-10 degrees. I would try running a good carb. cleaner (complete system cleaner) in the gas tank and top it off with some decent gas and see how that does, when you use the cheap gas again. If it still is acting that way, pull back the timing to 9 or maybe 8 degrees, and see if that helps. You didn't say how much compression that you have. Also, one last thing, what about your idle, is it too high? I had to have my idle higher on my Chevelle when I changed cams, so I would just shut off the motor in gear (end of dieseling).- Steve</font color=blue>

    <font color=blue>Steve Sosa a.k.a. "sosaman"</font color=blue>
    http://sosaman.home.texas.net/carpics.html
     
  7. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Could be sticky needle and seat causing the float level to be too high and an overly rich condition. Hows your mileage? I would go with the carb cleaner method first, and if that did'nt fix it I would remove the top of the carb and check the needle and seat and float level.

    Rene

    [​IMG]
     
  8. realsquash

    realsquash 1/2 ton status

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    Pull the spark plugs and see if you've been running too rich or if they are oil fouled. If you've got a lot of carbon buildup in the combustion chambers, 92 octane fuel will cover up the pre-ignition problem caused by the hot carbon. Been there, done that! Forget the fuel pump thing, I didn't think about it hard enough!

    Squash
    http://www.trailrunners4x4.org/users/realsquash
     
  9. Burt4x4

    Burt4x4 3/4 ton status

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    Cool, Thanks guys!
    I will order a rebuild kit for it and clean the carb!
    At the same time put in my 6A box and re adjust timing and air/fuel mix.

    hmmmm, wonder if I should do the ATF trick first, before I tear it down??? on that note does the motor need to be nice and HOT when doing the ATF thru the vac port cleanout trick??
    Thanks!!

    Rock ON![​IMG] 72 K5 [​IMG] Led Zeppelin
    http://burt4x4.coloradok5.com
     
  10. Shawn

    Shawn 1/2 ton status Premium Member Author

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