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#1 bryan 110 OFFLINE  

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Posted May 25, 2017 - 04:49 PM

Why dose my case 446 with Onan only fire on one cylinder. Has great compression spark on both sides and gets gas both sides. The silly thing is it will not fire on both sides....... What the dilly is going on?
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#2 Oldford OFFLINE  

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Posted May 25, 2017 - 04:55 PM

Did you check compression?  they can break a rod and still run on 1...


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#3 bryan 110 OFFLINE  

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Posted May 25, 2017 - 05:08 PM

Has great compression. I know the onans can run split in half we had a bobcat that did that had no idea it broke until turning around and say hay where'd the oil com from. And I mean this thing was split like it was in two parts.... But yes the case has great compression in both cylinders
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#4 637Yeoman OFFLINE  

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Posted May 25, 2017 - 05:13 PM

Why dose my case 446 with Onan only fire on one cylinder. Has great compression spark on both sides and gets gas both sides. The silly thing is it will not fire on both sides....... What the dilly is going on?

Sure its not a one cylinder?  :D  :wave:



#5 GardnMastr OFFLINE  

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Posted May 25, 2017 - 05:53 PM

The Onan ignition fires with one coil for two cylinders. It jumps the sparkplug normally on one side goes through the block and jumps backwards on the other side.  Thus it completes the circle beginning and ending at the coil. You of course know a typical briggs and stratton fires every time the piston comes up. Even though it is a 4 cycle, it fires every time like a 2 cycle, every other spark accomplishing nothing. The side of the Onan on compression fires and the opposite side does nothing. If you had a sparkplug with the electrode touching the center part, your Onan would run like a single cylinder instead of a twin. Or somehow the ignition is completing the circle without going through one sparkplug, Say perhaps a sparkplug wire was shorted to the block.


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#6 Cvans ONLINE  

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Posted May 25, 2017 - 06:08 PM

Fouled plug?



#7 MiCarl ONLINE  

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Posted May 25, 2017 - 06:14 PM

Fouled plug?

 

I need to point out that a fouled plug will often fire laying up against the engine when it won't work in the cylinder.

 

Swapping the plugs would be one way to rule that out.


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#8 gopher OFFLINE  

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Posted May 25, 2017 - 06:33 PM

:ditto:


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#9 Xrperry ONLINE  

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Posted May 25, 2017 - 06:46 PM

Mine did the same thing, had a massive vacuum leak on intake manifold
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#10 secondtry ONLINE  

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Posted May 25, 2017 - 07:18 PM

I would just replace both plugs to se what happened. Plugs being relativly cheep and having spares so handy. Don


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#11 bryan 110 OFFLINE  

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Posted May 25, 2017 - 07:55 PM

Thanks guys will try this out!

#12 ssmewing OFFLINE  

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Posted May 25, 2017 - 08:43 PM

Spark testers are about $10 and nice to have.

 

I had the same thing once and it was the condenser. I only will use the Onan Condenser.


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#13 jimmy G ONLINE  

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Posted May 26, 2017 - 08:17 AM

Try a plug and wire frist,if this dose nothing than its the coil,twin legged coil ignition is called waste spark,when the coil gets weak it will take the path of least resistance(shortest wire usually),I have seen this happen on snowmobiles and car's alike
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#14 bryan 110 OFFLINE  

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Posted July 30, 2017 - 12:42 PM

Still poppin on one cylinder! It will hit on both if the choke is on but if it's off notta. Changer plugs wires are ok might change them but get really good spark at plugs so not worried please help

#15 KennyP ONLINE  

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Posted July 30, 2017 - 01:40 PM

Might be the intake is sucking air at the seam on that side! Been known to happen to these! With the choke on, you richen the mixture enough it will fire.






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