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Bobcat 250 2002 model onan engine HELP

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  • Bobcat 250 2002 model onan engine HELP

    I've got a bobcat 250 with an onan engine welds great for a few hours then starts miss and cut out will barely run. Few minutes takes off running again and will keep repeating processs don't want to keep throwing expensive parts at it.

  • #2
    It's safe to say it's either fuel or ignition and the fact it goes a "few hours" before acting up would lead me to think ignition as in coil or crank module breaking down due to heat.

    I would think if a fuel problem it would show up much quicker than hours of running but with a crankcase pulse type fuel pump I would make sure the oil level is correct as a low oil level can effect fuel pump performance.

    The fact the problem will somewhat correct itself after the unit sits for awhile makes long distance troubleshooting a bit more challenging.

    Do you have an Onan engine manual that you can refer to for ignition and fuel system troubleshooting/testing? If not, PM me an email address as the .pdf file size is too large to post here.
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    • #3
      Originally posted by duaneb55 View Post
      It's safe to say it's either fuel or ignition and the fact it goes a "few hours" before acting up would lead me to think ignition as in coil or crank module breaking down due to heat.

      I would think if a fuel problem it would show up much quicker than hours of running but with a crankcase pulse type fuel pump I would make sure the oil level is correct as a low oil level can effect fuel pump performance.

      The fact the problem will somewhat correct itself after the unit sits for awhile makes long distance troubleshooting a bit more challenging.

      Do you have an Onan engine manual that you can refer to for ignition and fuel system troubleshooting/testing? If not, PM me an email address as the .pdf file size is too large to post here.

      Agreed. First drain and refill engine oil. Use 10w30. Will take 2 quarts with filter. Then replace igntion coil. You can also ohm the coil. However it must be hot...so ohm it when its cool. Run the unit once it shuts off ohm it again.
      Kevin
      Lincoln ranger 305g x2
      Ln25
      Miller spectrum 625
      Miller 30a spoolgun
      Wc115a
      Lincoln 210mp
      F550 imt service truck

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      • #4
        Thank you

        Originally posted by Tryagn5 View Post
        Agreed. First drain and refill engine oil. Use 10w30. Will take 2 quarts with filter. Then replace igntion coil. You can also ohm the coil. However it must be hot...so ohm it when its cool. Run the unit once it shuts off ohm it again.
        Kevin
        We have changed everything but the coil will change it today thank you

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        • #5
          Yesterday when it did it I was pretty well done welding. For the first time it ran so bad I had to choke it to keep it running. After playing with the choke a few seconds it took off and ran. I didn't have anything to weld on so I let it run on high idle for around an hour then switching to low idle turning off back to high idle just to change things up never messed up. Today when I messed up for the first time I jacked with the choke got it to take off and run then switched it to high idle no issues yet

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          • #6
            New COIL AND STILL NO GOOD

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            • #7
              Originally posted by Rockin n View Post
              New COIL AND STILL NO GOOD
              Well your story changes. Before it would run for a few minutes then die. Then would restart aftet sitting. Thus leading to coil. If you had ohmed it like i told u to it would have shown it was fine.
              If the unit is running on choke on, then you have a fuel probelm either the csrb is dirty and plugger or you neef to do a carb clean and rebuild. Also possible u have a cracked pickup tube.
              Kevin
              Lincoln ranger 305g x2
              Ln25
              Miller spectrum 625
              Miller 30a spoolgun
              Wc115a
              Lincoln 210mp
              F550 imt service truck

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              • #8
                Originally posted by Tryagn5 View Post
                Well your story changes. Before it would run for a few minutes then die. Then would restart aftet sitting. Thus leading to coil. If you had ohmed it like i told u to it would have shown it was fine.
                If the unit is running on choke on, then you have a fuel probelm either the csrb is dirty and plugger or you neef to do a carb clean and rebuild. Also possible u have a cracked pickup tube.
                Kevin
                Also be sure to check out the pulse fuel pump.
                Kevin
                Lincoln ranger 305g x2
                Ln25
                Miller spectrum 625
                Miller 30a spoolgun
                Wc115a
                Lincoln 210mp
                F550 imt service truck

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                • #9
                  Sorry thought I had it all right the first few days it runs about 3 hours like once it gets hot and will start missing and cutting out. Cuts out for a few min then takes off again runs great about ten min and repeats cycle. The last two days while cutting out has died a couple times and have been able to keep it running by playing with the choke. I didn't think it was fuel related due to it running do good for a few hours while cool. I really appreciate everyone's help.

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                  • #10
                    You could have something in the fuel tank that is getting sucked up to the pick up tube, starving the engine for fuel. Then when It quits, the piece of junk drops off of the pickup tube allowing fuel to flow again for a while until it gets sucked up again. Lots of possibilities for fuel problems, many that have already been mentioned.

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                    • #11
                      Onans seem to run really cold venturi temperatures. I've had to fight condensation building up in the air filter box on my Marquis genset and carb ice on some days. Is the air filter getting wet? Another issue I've had is when running Mobil 1, it foams in the Onan sometimes enough to trip the low oil pressure sensor.

                      80% of failures are from 20% of causes
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                      • #12
                        Seems to be running extremely hot oil looks good was told to change fuel lines said they could be expanding in the heat

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                        • #13
                          If you have to keep it running with the choke when the engine is warmed up, something is making the engine run way too lean. Others have suggested blockages, and you might also look for a vacuum leak that occurs when the engine warms up. Squirts of carb cleaner at suspect gaskets or other areas of possible vacuum leaks might find the problem; the engine will run different when the carb cleaner is sucked into a vacuum leak.

                          Changing fuel hose is a good thing to do routinely, some say every five years. Gasohol gradually degrades all fuel hose (other than very expensive Teflon racing hose), causing the inner lining to lose little chunks of rubber, which can plug carburetor passages. Welders, cars, trucks, boats, anything running gasohol should have the fuel hose replaced every so often. I'm not one of those who gets indignant about gasohol, but this is one thing to add to a preventive maintenance routine.
                          Last edited by old jupiter; 09-05-2015, 11:39 PM.

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                          • #14
                            I have an '06 . Runs great with the choke out a little. My son researched it on the web, he came back with the notion it is a leak in the intake manifold. It seems, though I haven't taken it apart, they were prone to that. Something about two non compatible metals bonded with some sort of epoxy substance prone to failure. I reiterate this is only hearsay, not fact.
                            Last edited by WillieB; 09-06-2015, 07:05 AM.
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                            • #15
                              The intake is next on the list but as of right know changing the fuel lines seems to be working.

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