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Problems with 16hp ONAN on miller bobcat

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  • Problems with 16hp ONAN on miller bobcat

    I've got the onan on my 225nt bobcat. The unit has right at 2000hrs on it. About 30 hrs ago it would not run, replacing the pickup behind the flywheel got it going, and replacing a weak coil got it running even better. Now it will run and start, but when using it as a generator, it will not kick the idle down when there is no draw. Sometimes it idles down, but then revs erratically. . . Not sure where to look on this one, what controls the idle kick down?? Also, smells rich, and the inside of the filter will be damp with gas if you take it off. Not sure which is cause and which is the effect. . . . Also, the unit doesn't charge the battery, have to leave it plugged in overnight every 3 weeks or so. . . . .

  • #2
    Originally posted by bottlefed89 View Post
    I've got the onan on my 225nt bobcat. The unit has right at 2000hrs on it. About 30 hrs ago it would not run, replacing the pickup behind the flywheel got it going, and replacing a weak coil got it running even better. Now it will run and start, but when using it as a generator, it will not kick the idle down when there is no draw. Sometimes it idles down, but then revs erratically. . . Not sure where to look on this one, what controls the idle kick down?? Also, smells rich, and the inside of the filter will be damp with gas if you take it off. Not sure which is cause and which is the effect. . . . Also, the unit doesn't charge the battery, have to leave it plugged in overnight every 3 weeks or so. . . . .
    These things need a GOOD battery and charging system to work properly. It's probably the voltage regulator (in the top of the RH cylinder shroud- looking from the flywheel end) Check the wiring to it. If you have an ohmmeter, check the regulator from the center terminal to each side terminal. It should conduct in one direction, but not the other.
    Make very sure the idle solenoid linkage is free. The solenoid has to bottom out when the arm on the carb touches the idle stop screw. If it works at all, it's probably sticky linkage or low voltage.
    These engines always seem to spray a little gas into the air cleaner as they shut down.

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    • #3
      Voltage Regulators go on these - cheap and easy to replace. Check on line. That would cover the battery charging and could explain the erratic operation of the idle down. Check your voltage when running- if it is over about 17 volts - your module needs replacing.

      Lots of things can affect the idle control. Start with the linkage as suggested below - follow the guidelines in the manual. If everything is good there - you need to check the sense circuits and then the idle control module. A little more difficult to diagnose. There is a full troubleshooting sequence in the technical manual if you can get access to one that steps you through it.

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      • #4
        I would second the voltage regulator, I had one go bad on a 225g and it blew the top of the battery off.

        The solenoid that the linkage is tied into has a very small hole in the end of it, opposite of the linkage, I found little dirt daubers will fill it full of mud and will not idle up (or is it down, have forgotten) but clean that out and give it a squirt of WD-40 and will work much better.

        Just a thought

        G3

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