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Dieseling?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Leadfoot, Mar 21, 2002.

  1. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    I recently purchased a 78 K10. I have been taking it to work each day (about a 25 mile commute) on the highway 70-75 MPH and bombing around town on the weekends. I never had a problem until last night when I plowed. Everytime I shut it down it would diesel (briefly). I looked at the temp guage and it was not even 200 degrees (sat at about 195) when shutting down but it still dieseled. I know plowing puts more stress on the motor and the plow doesn't help with air-flow through the radiator, but the temp quage was not hot. I'm assuming it is high combustion chamber temp causing the dieseling. Fuel igniting from heat and pressure rather than ignition spark. What are possible solutions and what do you guys think. I was thinking of going to a one step colder spark plug and/or going with a colder thermostat. Do these sound like a good idea or are there drawbacks? And it there any suggetions you have? Thanks in advance. It has a Carter carb of unknown size on it, and I was also thinking of maybe making some adjustments, i.e. richening just a hair to lower combustion temps, but I would like some input.
     
  2. Confederate9

    Confederate9 1/2 ton status

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    mine did that last summer, i changed the oil, oil filter, and put in gasoline treatment...... and then it didnt do it any more, i dont know why, jsut some things i tried off the top of my head and it worked!
    strange huh?
     
  3. dyeager535

    dyeager535 1 ton status Premium Member

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    Not sure if this would be present on our vintage truck, but on my '83 with AC, it had a "kicker" solenoid on the carb, presumably to raise idle when AC was on. It failed, and the truck would ALWAYS diesel when shut off after that. I unplugged it, and of course, the problem was solved. That was an easy fix, hope yours is as easy!
     
  4. BorregoK5

    BorregoK5 1/2 ton status

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    The heavier load on the motor might have a different effect on carbon buildup in the combustion chamber. Try upping to a higher grade of fuel and see if that helps, or running a heavy duty spark plug indexed to shroud the spark.
     
  5. Hossbaby50

    Hossbaby50 3/4 ton status

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    I have had this problem a couple of time. Once it was the choke on the carb was bad. Second time, I threw in some Lucas Upper Cylinder cleaner & fule system cleaner, and some 89 octane gas and it stopped. Periodically during the summers in AZ if I run the truck hard when it is hot, it will diesel when I turn it off.
     
  6. TopOff

    TopOff 1/2 ton status

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    Run two tanks of Chevron premium through it.

    I suspect it is carbon buildup in the pistons and or valves.

    Good Luck.
     
  7. JK5

    JK5 1/2 ton status GMOTM Winner

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    My 77 runs much better at 180, I had the same problem with my plow truck, do you have clutch fan, I removed it and put on a regular fan set-up! That seemed to fix the overheating problem I had.
     

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