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Thread: MEP531 Governor Problems

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    Default MEP531 Governor Problems

    My MEP531 starts up easily and runs, but it immediately starts to overspeed. The engine blows tons of smoke and pegs out the frequency gauge, and is obviously revving way too high.

    Clicking the "Stop" lever while holding the governor lever by hand, I can control the engine speed and get the frequency gauge down to 60-65hz. At that speed the engine sounds much better and the exhaust clears right up.

    I spent a couple hours today reading the TM and looking at my generator, but I have no idea how to fix it. I am new to small diesels, but based on the symptoms above I am thinking the governor fly weights are stuck or not working, and causing the engine to try to rev up as high as possible. Is there a way to diagnose this without disassembling the engine?

    It looks like the fuel pump lever is centered in the governor fork like it should be:
    Pump Lever.jpg


    I have tried every possible combination of spring positions, but the generator always overspeeds no matter how the springs are set. Also the image in the TM shows linkage arms with more holes than mine has so its not super clear how to put this part together, but as mentioned I tried every combination of holes.
    Governor Springs.jpgTM Settings.PNG
    Last edited by 79Vette; 01-06-2019 at 22:44.

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    From looking at the TM it appears...
    When running the governor spring puts tension on the governor lever turning it CW to accelerate the engine.
    The mechanical weight system inside the crankcase exerts pressure turning the governor level CCW to slow the engine.
    In normal operation when those two forces are equal the engine will run at a constant speed.
    Since the engine just over speeds it would seem there is an issue with the mechanical governor inside the crankcase not exerting any force on the governor lever allowing the governor spring to pull the lever to full throttle.

    If it were mine... I'd disconnect/remove the governor lever assembly and springs completely.
    Then start the engine and feel it there is any apparent force being exerted by the mechanical fly weigh system to turn the governor lever CCW. I suspect you won't feel any force based on your description of what you've done and found.
    If no force is felt at various RPM's then I'd suspect there is an internal issue require tearing into the crankcase and examining the governor weights and thrust collar #9 that transfers the fly weight weight movement to the governor lever #10 inside the engine.

    Just my $0.02 this evening
    Attached Images Attached Images
    MEP-831A Governor Controller Replacements for the SLC100, 2990-01-477-1371, 98-19539.
    https://www.steelsoldiers.com/showth...49#post2176649
    MEP-802A, Two MEP-831A's

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    Just out of curousty losen the screw that pulls the govern springs it is the 10mm head with locknut above governor spring first!

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    Quote Originally Posted by kloppk View Post
    Since the engine just over speeds it would seem there is an issue with the mechanical governor inside the crankcase not exerting any force on the governor lever allowing the governor spring to pull the lever to full throttle.
    This was my assessment as well. Because I can "govern" the engine by hand with the springs disconnected and get it to run right, I dont think there is anything wrong with the engine itself or with the fuel system. I didnt think to pay attention whether the internal governor mechanism was exerting force on the lever, but if it was it could not have been nearly enough to overcome the springs or I would have noticed it.
    I suspect the governor flyweights are sticking, and thus never moving outward and pulling against the springs to slow the engine down. The engine had no oil in it when I got it so I guess it is conceivable there is some light rust or something in there causing the mechanism to stick. I was hoping someone would know something I overlooked that would save tearing into the engine, but it seems like that is what I need to do.


    Quote Originally Posted by profo View Post
    Just out of curousty losen the screw that pulls the govern springs it is the 10mm head with locknut above governor spring first!
    The only screw I know about that can be adjusted is the fuel limiter screw. I checked the adjustment on it and it seems fine, and I dont think it would affect the no-load overspeeding problem I have. Is there another screw I am missing?
    Hard Stop Screw.PNG
    Last edited by 79Vette; 01-06-2019 at 22:56.

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    I just went through this. Drain the oil and look in bottom of base and see if you find spare parts. Mine slung gov apart inside engine. It's part number 9 in diagram.

    I'll try to find the pix I took.
    Attached Images Attached Images
    Last edited by strycnine; 01-07-2019 at 22:17.
    M35A2 (sold)
    (2) MEP-016D
    (2) MEP-531A
    4A032-4


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    Sergeant Major strycnine's Avatar
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    Got the pins out when I drained the oil. Later I took the side cover off and got the rest of the parts out.

    Replacement part number 714770-61700. I got mine here https://www.comfortairgr.com/shop/go...-714770-61700/

    If I'm off base carry on
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    Last edited by strycnine; 01-07-2019 at 22:14.
    M35A2 (sold)
    (2) MEP-016D
    (2) MEP-531A
    4A032-4


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    Quote Originally Posted by strycnine View Post
    If I'm off base carry on
    I bet you are exactly right, based on the symptoms I have. I am a little sad that the engine seems to have puked the governor all over the inside of the crankcase with less than 3 hours on the clock, but it seems like that is the case. I guess it was surplused for a reason...

    I am up to my eyeballs working on my M1009 daily driver this week and probably most of next week too, but I will open the engine up as soon as I get some time and post back here with what I find.
    Did you need any new gaskets when you removed the cover?
    Last edited by 79Vette; 01-08-2019 at 04:15.

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    Sergeant Major strycnine's Avatar
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    Quote Originally Posted by 79Vette View Post
    I bet you are exactly right, based on the symptoms I have. I am a little sad that the engine seems to have puked the governor all over the inside of the crankcase with less than 3 hours on the clock, but it seems like that is the case. I guess it was surplused for a reason...

    I am up to my eyeballs working on my M1009 daily driver this week and probably most of next week too, but I will open the engine up as soon as I get some time and post back here with what I find.
    Did you need any new gaskets when you removed the cover?
    I reused the case gasket, but I'd recommend getting one.
    M35A2 (sold)
    (2) MEP-016D
    (2) MEP-531A
    4A032-4


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    Quote Originally Posted by 79Vette View Post
    I bet you are exactly right, based on the symptoms I have. I am a little sad that the engine seems to have puked the governor all over the inside of the crankcase with less than 3 hours on the clock, but it seems like that is the case. I guess it was surplused for a reason...

    I am up to my eyeballs working on my M1009 daily driver this week and probably most of next week too, but I will open the engine up as soon as I get some time and post back here with what I find.
    Did you need any new gaskets when you removed the cover?
    You are assuming! Don't assume. Look when you get a chance. I had one come in with paper towels in the crank case, and I think someone else here in the forum did too.

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    You adjustment screw looks suspicious to me the locking wire is missing. Might want to look into it closer
    MEP-831A MFD-2005
    MEP-831A MFD-2002 Reset 2006 @2.2hr
    MEP-531a MFD 12-14 Dewey

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