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JLG 40H engine issues...

Discussion in 'Other Construction/Demolition Equipment' started by TonyStuart, Aug 20, 2015.

  1. TonyStuart

    TonyStuart New Member

    Joined:
    Aug 19, 2015
    Messages:
    2
    Location:
    Kintnersville, PA
    Thank you in advance for your help. I have a JLG 40H 4WD with a Ford LRG 425 dual fuel engine. I believe there are multiple problems so I will try to include all the info I can. The engine has been running sporadically. When it ran last all operations functioned properly. The engine would start and run at high (too high) rpm occasionally. Governor actuator appears to be working as it should. Carb has been rebuild several times with no change. Governor actuator linkage was adjusted to spec and rpm's were normal on gasoline but not on lpg. When it ran (well) it would run flawlessly for about five minutes and the engine would shut down. Thinking there was a safety shut off (oil press. or engine temp) issue, I tested the temp sensor and its in spec. Checked oil and it was 2 quarts over full, drained excess.

    Now, engine won't start. It turns over and fires every couple seconds but won't quite get going on gas or lpg. Definitely combustion at times while turning it over. Plugs show spark but I'm not sure if it is strong. Fuel pump moves gas well. Air filter is clean. Cam timing checked, but didn't look at oil pump sprocket. Spark plugs are wet after starting procedure. New plugs and wires. DIS harness checks per manual all good except engine spark advance circuit showed open on all three leads. Coil primary .9 ohms. Coil secondaries 13.9k ohms each. Ground connections good. Haven't checked compression yet (waiting on adapter), but when it ran it purred.

    I'm stumped... Any thoughts?

    Thanks again
     
  2. TonyStuart

    TonyStuart New Member

    Joined:
    Aug 19, 2015
    Messages:
    2
    Location:
    Kintnersville, PA
    Magically running again without changing anything... Now back to original problem. Engine will start and run for 5 - 10 min with all operations functioning. Start from ground controls and engine runs at medium/high RPM. Switch to platform control and RPM's drop to a high idle. From platform, step on dead man switch and RPM's jump to high. As the engine warms up stepping on the dead man's switch makes the engine race and when load is applied (boom lift) the engine immediately dies.

    My next step is to check vacuum hoses and vacuum sender. Then pot settings on the electronic governor controller, although I have yet to see them. Maybe they are on the back of the unit.

    Any direction you can provide would be great! Thank you
     
  3. Joesair

    Joesair New Member

    Joined:
    Jan 14, 2021
    Messages:
    2
    Location:
    Vancouver
    Hi there,
    I have 1989 40H JLG and it has exactly the same symptoms as yours and would really appreciate some feedback or anyone familiar with this problem please help
    Thank you
     
  4. Topman

    Topman Member

    Joined:
    Apr 15, 2021
    Messages:
    6
    Location:
    Abbotsford, B.C.
    If you see my post in the telehandler section I had many issues with the engine not starting or starting but not staying running.
    I finally narrowed it down to the carb constantly flooding. There was a fuel pressure regulator installed but it was stuck wide open.
    After I cleaned and adjusted the regulator, the engine now starts and runs well. Oh and I also adjusted the choke mechanism.
    HTH.