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Discussion Starter #1
I'm hoping someone out there is willing to help me solve an intermittent problem with my 16hp Onan. Twice in the last 4 weeks I've started the tractor and it ran normally for about 4 or 5 minutes . . . but then it pops a few times out of the muffler and winds down toward a rough idle momentarily, and then stops. The key will not turn the starter, not even a click. There is an odd smell that comes from around the engine, maybe a burnt smell, but not one I'm familiar with. My neighbor showed me how to touch a jumper wire from a post on the ignition module to the battery - it then will crank normally but will not start the engine. Your guess is as good as mine as to whether it will start tomorrow.

I believe all of the normal maintenance requirements are up to date, including fairly new points and condenser. I can't seem to find any loose or damaged wiring. When it's in the mood to function, the tractor runs and operates perfectly (well, for an old and very used tractor).

Sorry I don't have any more clues to offer - it's not much to go on. Is the issue heat related? If so, why would it sometimes work fine?

Thanks in advance for any guesses you might have.
 

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It sounds to me as if you have some wiring problems that are not likely to be difficult to fix but can be tricky to isolate if you're not familiar with such things. When you say you are jumping a wire to the "ignition module" and it turns over I believe you are referring to the solenoid not the ignition. Since it will turn over that means the starter and battery are ok so there are two wires both or either of which could be causing the problems. One is the wire from the ignition switch to the solenoid--usually yellow and the other is the wire from the ignition switch to the coil. You should obtain a copy of the wiring diagram that will be in your owners manual or you can download a parts manual from the Ingersoll tractor web site and that also contains a wiring diagram.

When the key is in the run position you should have 12 v going to the + side of the coil and with the key in the start position you should have 12 v going to the solenoid via the yellow wire. If you check and don't find that is happening then you need to examine the wires to see if they are damaged or have bad connections, i.e. loose or corroded. It is also possible that the ignition switch is bad.

If you are not familiar with trouble shooting such things a friend who has experience working on engines should be able to help if you have a copy of the wiring diagram and these comments.
 

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You should validate the wiring carefully, but don't overlook the possibility of ignition switch itself. Look at the connector on the switch ... any evidence of recent melting is a sure sign the switch is a potential gremlin. Might also catch the switch being hot right when the motor shuts down.

These swtiches are not known to be as robust as the tractor ...

Brian
 

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Discussion Starter #4
Thanks for the response. I have the wiring diagram in the owner's manual, and with your advice printed and in hand I will see if my neighbor can help me trouble shoot tomorrow.
 

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Discussion Starter #5
Just one more question: would a bad ignition switch cause the tractor to backfire and shut down as it warms up?
 

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If the ignition switch is faulty and interupts voltage going to the coil, backfiring can result. You also may have a bad coil. However, a bad coil will not prevent the engine from turning over. For that reason, the focus should be on the wiring, the ignition switch, the fuse holder and the ammeter. Make sure all items are in good working order and that all connections are clean and tight. All voltage passes through the fuse holder and the ammeter. Both items can go bad so inspect them carefully.
 
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