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Isuzu 4LE2 RPM

Discussion in 'Generators/Gensets' started by 92U 3406, May 24, 2018.

  1. 92U 3406

    92U 3406 Senior Member

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    Working on a little MMG25 Magnum with a 4LE2 Isuzu (fully mechanical). Engine will not maintain 1800 RPM under load to generate 60Hz. So far fuel supply seems ok, intake is ok. Checked valve lash. #1 exhaust valve was tight so set it at spec. Loaded it up and burnt all the carbon out of the exhaust. If I grab the lever on the side of the governor it easily picks up RPM to spec under 100% load so lack of engine power doesn't seem to be an issue. Right now it drops about 70-75 RPM between zero load and 100% load. None of our other units with this engine drop off RPM like this. Is there an adjustment on the governor to tighten up the speed droop?

    Any help would be appreciated
     
  2. Birken Vogt

    Birken Vogt Charter Member

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    I have been told that a groove can form in the governor somewhere from running at a 1800 RPM for years and years and lead to this symptom. But so far no customer has wanted to pay the cost and fix it.

    However, 75 RPM droop is well within what I would consider normal. That is 62.5 Hz no load to 60 Hz loaded, I would expect that from a brand new unit.

    If you do dig into it, make note so I can see what is in there better.
     
  3. 92U 3406

    92U 3406 Senior Member

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    I figured there was something up with the governor. Its got over 10,000 hours on it so its quite possible the governor is worn. I just wanted to make sure there wasn't something simple I was overlooking. I cranked it up to about 1860 RPM no load and at 102% load it sits around 1780. I don't get any more "Gen Under Frequency" shutdowns now with the RPM turned up.

    I will get some photos for you if I do end up taking it apart.
     
    Simon C likes this.
  4. tool_king

    tool_king Senior Member

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    Sound like your governor might be worn a bit .Did you get it set so you have 60hz electrical output? It is permissible to turn it up a bit to get set right .I had to do it on a few gensets with many hours on them .
     
  5. DB2

    DB2 Senior Member

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    Not sure if it’s relatable but I had a C240 that would lose power and in the end it turned out the shut off solenoid was improperly adjusted and not allowing full travel to the run position. Burned up a few follicles on that one.
     
  6. 92U 3406

    92U 3406 Senior Member

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    I haven't had a chance to look at it since I posted. Might get around to it next week unless someone else jumps on it.
     
  7. Simon C

    Simon C Well-Known Member

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    We had some 4LE-2 Isuzu Gen sets with worn governors in Fort McMurray. But 59.8 Frequency is still good at full load. If old fuel I've seen some drop to the point of stalling with less than 100 % load. Can't say I've worked in one of these govenors. Simon