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Onan Help


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#1 suburban 12 OFFLINE  

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Posted March 26, 2014 - 07:47 PM

I just traded my brother a few days ago for his ss16. He had it most of the way to getting it running again. I cleaned the points and used some starting fluid and it started right up on old gas. I put some new gas in it and it was running fine. I started it up today and it is missing on one cylinder, not always but often enough that I can tell that it isn't running at full power. Is there anything specific that I should check/clean/replace first? I know that it isn't the coil, points, or condenser since it is running. I am planning on putting new spark plugs in it first. Is there a chance that it could the plug wires, points, or condenser?



#2 olcowhand OFFLINE  

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Posted March 26, 2014 - 07:53 PM

Been many a time that a plug wire was at fault.  



#3 propane1 OFFLINE  

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Posted March 26, 2014 - 08:52 PM

Plugs first thing to do. And make sure the right ones for the engine. Noel

#4 KennyP ONLINE  

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Posted March 27, 2014 - 05:35 AM

I had a similar problem on the Onan in Big Bertha. The tractor had sat for a few years. At idle, it would miss. Rev it up and it would fire. Finally decided rings were stuck in that cylinder. Put some MMO in the cylinder and crankcase and let it sit a few days. Fired it off and let it run at a good RPM till it warmed good. Took several times of doing that, but it runs fine now!


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#5 suburban 12 OFFLINE  

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Posted March 27, 2014 - 06:21 AM

Its not just missing at an idle, it is missing when I rev it up. Tuesday, I could put the throttle at an idle and it would sit and idle just fine. Yesterday, I put it at an idle and it would stall.

 

Were can I find new plug wire for it?



#6 KennyP ONLINE  

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Posted March 27, 2014 - 06:31 AM

Have you swapped the plug wires at the coil to see if that makes a difference?



#7 suburban 12 OFFLINE  

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Posted March 27, 2014 - 08:02 AM

No, I haven't. I am not sure which cylinder it is missing on.



#8 ol' stonebreaker OFFLINE  

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Posted March 27, 2014 - 09:12 AM

I had the same problem w/ the onan on the welder I acquired last fall and found the float needle had a small piece of crud in it causing the fuel level to be too high causing it to miss at high RPM and flood and die at idle.
HTH,
Mike

#9 suburban 12 OFFLINE  

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Posted March 27, 2014 - 10:55 AM

Thanks. That actually sounds like it could be the problem. I started it on old gas for the first time in I dont know how many years. It didnt have much left and it almost ran out before I put more gas in, so it could have sucked a piece of dirt out of the tank. I will try new plugs first anyway since the ones in it are old. How hard is it to get to the float needle?



#10 olcowhand OFFLINE  

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Posted March 27, 2014 - 04:56 PM

The pulse fuel pumps built onto the carbs over time will build up with crap at the diaphragm.  If any of that breaks loose, there is nothing between it & the needle, so it could foul the needle easily.



#11 suburban 12 OFFLINE  

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Posted March 27, 2014 - 08:05 PM

I am starting to think that that is the problem. I started it up today and it started out running rough. I revved a few times and I must have gotten it to shake loose since it started running right after that.  






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