John Deere M - Cutting out under load
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Thread: John Deere M - Cutting out under load

  1. Top | #1

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    04-21-2018 @ 10:31 PM
    Graham WA
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    John Deere M - Cutting out under load

    When I'm in the field driving a 5' finish mower and turn to go up a slight grade, the engine has recently started to cut out (like it's starving for fuel). Initially, I thought maybe the fuel level was low in the tank and it wasn't getting picked up, but, the fuel bowl type filter is full and plenty of gas in the tank.

    As a note; I had recently went through and replaced all ignition components (because of a stumble and mis-fire issue), less the coil. I didn't have this completely cutting out problem before or after the ignition work, so I don't think it's ignition related.

    My engine compression is about 110 on both cylinders. Don't know what compression readings should be, but that does not seem unreasonable for a well used 8-to-1 ratio engine. It does smoke a little, which seems worse on startup when hot (probably valve guides). It does not use any significant amount of oil however.

    I'm thinking of ordering a carb rebuild kit.

    Does anyone have other ideas or experiences similar to this? If so, how were they resolved.

    Thanks for the help !

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    89420's Avatar
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    08-06-2019 @ 01:00 PM
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    well im not experianced with the M engine but i would look into the govener and see if its adjusted and working
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    Evergreen's Avatar
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    06-02-2017 @ 07:24 PM
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    Is your carb adjusted properly? I experienced a similar situation with my old Model G and it turned out that I had the main jet set too rich.

    However, I agree that the govenor is most likely the culprit.
    89420 likes this.
    '50 Model M w/electronic ignition, 12v conversion, and a 3pt conversion plus a homemade snowplow, a Deere Model 51 trailer plow, a Woods RM59 finish mower, a Bark Buster splitter, and a few other toys.
    '69 Sears Suburban 14 48" deck and 42" back blade, an estate rake, and a sweeper.
    '07 F250 XL Powerstroke, crew cab, short box, 4x4.
    '85 F150... I finally sold my very first truck after racking up over half-a-million miles on the original drivetrain.

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  6. Top | #4

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    01-16-2017 @ 02:18 PM
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    Engine governor has absolutely nothing to do with engine misfiring when load increases. The governor seems to be doing it's job properly by increasing the opening of the throttle valve in the carb.

    The problem could be ignition or carb related. Does pulling the choke out make the problem better or worse? If no different then the problem is most likely ignition.

    You don't list all the parts you replaced in the ignition system. A bad coil and bad condenser can cause high load misfire. Could be bad spark plugs, distributor cap and/or rotor, points, plug wires, use copper wire core wires only, and bad spark plugs. The quality of replacement parts for engine tune-ups today is DEPLORABLE! Many out of box defective parts.

    If the engine keeps trying to run under the increased load with the choke partially closed then you probably have a fuel starvation problem. A reassembly and cleaning should help that problem. You might try installing a vacuum gauge to the intake manifold and see if engine vacuum is low meaning there may be a vacuum leak somewhere between the carb and cylinder head causing the extreme lean condition when the carb opens up. A quick peek at the spark plugs would show the firing tips would be very white due to the lean condition in that situation.

    The main fuel adjustment on the carb may be lean since you had a misfire condition before replacing ignition parts. You might check the condition of the air filter and pipes/hoses running from the precleaner cap to the carb to make sure there's no restrictions of combustion air. It's not unheard of on these old tractors with oil bath air cleaners!

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