Cheese... 22.5 HP Onan NHC


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Old 12-02-19, 07:37 PM
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Cheese... 22.5 HP Onan NHC

So my old '77 Gehl skidloader has intermittent ignition problems. 2 cylinder engine. It has new points and condenser that probably only have 3-4 hours on them. Correctly gapped, timing is preset. (Ignition plunger rides directly on the cam)

Points don't always seem to be making contact when they close. Once it's running it runs fine... never misfires or quits. But every once in a while when you go to start it again, it won't fire... and once the cover is removed I find no spark across the points. (Especially easy to see at night) I dont think they are oily. To get it started again all I have to do is crank it over while jumping the points with a small flat screwdriver, it fires and will start.

Any ideas of what I should check? Some sort of intermittent ground maybe? Could the ignition plunger be worn down, throwing off the timing and dwell?
 
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Old 12-02-19, 08:18 PM
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That trouble sounds similar to bad bearing in the distributor. The cam doesn't rotate centered..... it moves a slight bit. You can set the points but as soon as the cam turns the point setting is off and they won't close.
 
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Old 12-02-19, 09:01 PM
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I guess I haven't tested the ignition coil primary and secondary resistance yet... should probably do that. But it just seems to me like it's simply a points contact problem. I've done the fine sandpaper trick, really hasn't helped. Maybe I just need to replace them again.
 
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Old 12-02-19, 09:22 PM
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Hmm... Its been a while since I installed the points and condenser (160-1183) but if memory serves, I don't believe that I made a point box gasket to put between the mounting plate and block. From what I just read, that gasket should be about .05" thick. Not sure if that has anything to do with it or not but I better do that. Without the gasket in, I suppose that throws things off slightly as well?
 
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Old 12-02-19, 10:33 PM
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I've got gaskets ordered (160-1368) as shim and heat sink... Found a suggestion to stack two of them to assist with setting the points. Will see how that goes.
 
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Old 12-03-19, 04:38 PM
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Might not hurt to test the connection of the points with an ohmmeter when it's not sparking. I'd also check the movement of the points, if they aren't moving enough, it may be that the plunger is worn down too short (if it runs off a plunger). If they run directly on a small cam lobe, that wouldn't apply.
 
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Old 12-03-19, 04:49 PM
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Yes, there is a plunger... haven't measured it yet. When you say test the connection (when no spark)... do you mean test them to see if they test as if they are still making contact when closed?
 
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Old 12-03-19, 09:51 PM
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Yes, check resistance to see if they are making contact or not.
 
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