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Injection Timing

Discussion in '1982-Present GM Diesel' started by calcide, Mar 30, 2002.

  1. calcide

    calcide 1/2 ton status

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    What is a good ballpark figure for timing on a 6.2? I measured mine today at 8 degrees and Parf's at 25 degrees. We used a piezo pickup (ferret model something or other), mounted to the same place in both trucks.
     
  2. calcide

    calcide 1/2 ton status

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    Well, does anybody know?
     
  3. arveetek

    arveetek 1/2 ton status

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    3-5 degrees BTDC is where it is supposed to be set.

    Oftentimes, the harmonic balancer marks get "relocated" over time, throwing off the readings.

    Casey
     
  4. René

    René 1/2 ton status

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    I adjusted the timing after hearing. Between the markings on the pump flange and the cover are now 0.12 in.
     
  5. DieselDan

    DieselDan 1/2 ton status

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    Yep, factory was like 3 or 4 degrees. Didn't one of the Four Wheeler magizines do an article bumping up the timing to like 6 or 7 degrees.

    I've run into that timing oddity thing, on a low mileage CUCV. The timing was like 24 degrees or something! Couldn't figure out why we got this reading, but it ran good so we left it alone.
     
  6. René

    René 1/2 ton status

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    Very strangely!?
    But in the meantime nothing more surprises me.
     
  7. calcide

    calcide 1/2 ton status

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    Here's another question: When we adjusted his timing, there was not very much change when the pump was rotated. The best we could get it to was 14 degrees. It ran a lot better, but should there be more adjustment?
     
  8. DieselDan

    DieselDan 1/2 ton status

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    If you were using a diesel timing tool, did you have an "offset" to add/subtract to the actual reading? OR was the engine fully warmed up (HPCA not activated). Maybe disconnect the HPCA (pink?) wire to be sure the cold advance isn't on.

    I've adjusted small diesels (VW, Isuzu, Onan) by ear and been damn close, but the 6.2s seem insensitive (at idle) to injection timing. Them four (and three) bangers can really shake!
     
  9. René

    René 1/2 ton status

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    Pink is the wire to the fuel solenoid. You disconnect it and the engine is off. Green is the right one (HPCA).
    With most cars, 5° more or less makes not a different. Not so with some GM Diesel. If I place the pump very in advance, the engine doesn't start any longer. The best adjustment for my engine are 4°. I turned the pump so long on advance, until the engine ran clearly more softly, then again somewhat back...
     

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