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Bobcat 225 NT (Onan motor) runs for a Few Minutes, Then Dies


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  #1  
Old 06-20-2019, 08:29:29 PM
DukeNukem DukeNukem is offline
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Default Bobcat 225 NT (Onan motor) runs for a Few Minutes, Then Dies

When my 225NT is cold, it cranks and runs great for 5 minutes and then suddenly dies.
I've tested and it's cutting power to the coil for some reason.
I've replaced the coil, condenser and crossed the low oil sensor.
Anyone have any ideas?
SN: KK215899
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Old 06-21-2019, 02:28:11 AM
cobbadog cobbadog is offline
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Default Re: Bobcat 225 NT (Onan motor) runs for a few minutes, then dies.

Fuel supply?

Is there a good steady supply of fuel to the engine?

Try again and have a can of either with you and when it starts to die spray a small amount into the sir intake. If it picks up you have a fuel issue if not you have a spark problem.

Have you tested your spark immediately after it stops?
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Old 06-21-2019, 07:02:48 AM
DukeNukem DukeNukem is offline
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Default Re: Bobcat 225 NT (Onan motor) runs for a few minutes, then dies.

Quote:
Originally Posted by cobbadog View Post
Fuel supply?

Is there a good steady supply of fuel to the engine?

Try again and have a can of either with you and when it starts to die spray a small amount into the sir intake. If it picks up you have a fuel issue if not you have a spark problem.

Have you tested your spark immediately after it stops?
I'm getting plenty of fuel. The spark just stops completely. It's exactly the same every time I start it.
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Old 06-22-2019, 01:29:01 PM
dkamp dkamp is offline
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Default Re: Bobcat 225 NT (Onan motor) runs for a few minutes, then dies.

We had similar experiences with our Lincoln Ranger 8's with Onan Performer 18s in our service trucks.

We found that adding a whole lotta ventilation alleviated the problems, but there was disputed theory as to WHY they shut down...

I would not be surprised if a low-oil-protection device, a temperature switch, or even a failing kill switch were the problem... but the strange thing is, that I had opportunity to rescue a Bobcat 225NT that had it's undercarriage all rusted out.

I removed the rusted stuff, made a new chassis, and omitted the fuel tank (used a remote fuel tank and battery), and used it in my service truck instead of the Rangers, and it never exhibited any overheating... which is only part of the story...

Long before shutting down, the Rangers would start to lose welding power after a while... my guess is that the windings were probably getting warm... the Bobcat would NOT lose welding power or shut down.

I believe, however, that my Bobcat had it's ignition switch replaced at some point... so they may be a weak point... so I'd recommend checking that first.
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Old 06-26-2019, 07:59:00 AM
Peter Holmander Peter Holmander is offline
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Default Re: Bobcat 225 NT (Onan motor) runs for a few minutes, then dies.

Hey dkamp !! I sent you a private message. Take a peek at it when you get a chance. Thanks.
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Old 06-27-2019, 06:28:50 PM
Tracy T Tracy T is online now
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Default Re: Bobcat 225 NT (Onan motor) runs for a few minutes, then dies.

only other thing thats not be mentioned that i can think of, possible the coil it self is failing when it gets warm? acts just like a condensor but you have already replaced that....
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Old 06-28-2019, 07:52:10 AM
cobbadog cobbadog is offline
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Default Re: Bobcat 225 NT (Onan motor) runs for a Few Minutes, Then Dies

Yep a coil can fail after it has been running for a while. On my ignition tester I use for the flywheel magnetos on our mowers it has a function to 'heat' the coil for 5 minutes and re test the coil so it is a possible problem.
Still check the function of the ignition switch and any other fail safe switches with the multimeter. Using the multimeter on the coil may not show that it fails under load and is why a tester is used to get it warm.
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