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Onan JC - Problem With My “Very Reliable” 15JC-3R/3998L


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  #21  
Old 02-07-2018, 07:12:31 PM
Max Thompson Max Thompson is offline
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Default Re: Onan JC - Problem with my “very reliable” 15JC-3R/3998L

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Originally Posted by Billy J Shafer View Post
It has no timing chain. It is gear to gear. Timing could be off or a valve problem. I would also make sure the vents on the fuel system are clear. Also check over the ignition system.
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Originally Posted by Leon N. View Post
Interesting! Blew the dip stick out! I would suspect somehow propane is getting into your crankcase. How could that occur? Via the carburetor cc breather or a malfunctioning KN regulator or a combustion chamber malfunction. I suspect when the JC backfired it set off the combustible mixture in the cc. Maybe your gas regulator is not properly set?
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On the Garrettson regulator, there is a small VENT that is on the outside edge of the regulator. It is a brass fitting with a small screen pressed into it. Check it to make sure it doesn't have an obstruction.
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Originally Posted by Leon N. View Post
My first thought that comes to mind is a fuel problem. Too much or too little gas into the carburetor. I can get all sorts of erratic operation by miss adjusting the fuel supply. In 48 years of use, I have never had a need to re adjust the valves.
I would check all the above first. The set had been running fine up until it quit. I assume you were not standing beside it when it quit, so you do not know exactly what transpired.

The excessive back fire could have damaged something else, agreed. A compression test is quick and easy and will eliminate many questions. While you have the plugs out, you can use a test light to check static timing, this is a simple procedure and is covered in the service manual.
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Old 02-08-2018, 08:36:46 AM
PopsGarage PopsGarage is offline
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Default Re: Onan JC - Problem with My “Very Reliable” 15JC-3R/3998L

Propane gas is heavier than air, the slightest leak in the gas train will allow gas to flow into the carburetor and then into the engine, it could fill a cylinder and leak past the rings into the crankcase....

Bob
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Old 02-08-2018, 11:09:02 AM
Leon N. Leon N. is offline
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Default Re: Onan JC - Problem with My “Very Reliable” 15JC-3R/3998L

With all due respect to everyone, I got a feeling he has either a fuel supply problem or a component failed. Could be anything all the way from the gas regulator to a failed spark plug wire or something in between. Can not wait to hear!
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Old 02-08-2018, 11:21:06 AM
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Billy J Shafer Billy J Shafer is offline
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Default Re: Onan JC - Problem with My “Very Reliable” 15JC-3R/3998L

I agree Leon. Running fine now doesn't. Check the simple things first.
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Old 02-08-2018, 02:34:43 PM
Leon N. Leon N. is offline
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Default Re: Onan JC - Problem with My “Very Reliable” 15JC-3R/3998L

Hey Billy how are you doing these days. I recall you had a touch of pneumonia back a while ago. I hope you are OK now.

I thought of you last week when I developed a wicked stomach ache. Turns out I had a gall bladder attack and the doc checked me all over, the vitals were all normal, so he decided just watch it and see if it goes away, better than going in for surgery. Well this week I am feeling much better, funny thing though, the pain sometimes returns but in decreasing intensity. Being 80, I do not want surgery if it can be avoided. Got to watch what I eat..

Also funny thing but I always fee better after reading Smokstak. Seems to be good therapy. Am I crazy or what?

Leon
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Old 02-08-2018, 03:04:51 PM
JohnnyC JohnnyC is offline
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Default Re: Onan JC - Problem With My “Very Reliable” 15JC-3R/3998L

Leon, in my list of medical issues I had my gall bladder removed in 2011. 3 days of pain after the surgery. They put 3 (or was it 4) holes in me including one through the belly button to remove it. A simple ultra sound like the type they use on women to see the baby is all they need to see the stones. The pain will come unexpectantly and last for various lengths of time then go away. Stay away from greasy foods.

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Old 02-08-2018, 03:26:10 PM
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Billy J Shafer Billy J Shafer is offline
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Default Re: Onan JC - Problem With My “Very Reliable” 15JC-3R/3998L

Leon I got over that and then had a stroke #3. That Agent Orange last along time. Of course the V A tells all us nam vets. We don't have any problems.

Other than that doing ok. I think that since I can't see well enough to drive and work. I will spend more of my time at the stak. Pass on more of my great knowledge. Of course I will have to find it first. Maybe become the head BSer
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Old 02-08-2018, 03:57:06 PM
Leon N. Leon N. is offline
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Default Re: Onan JC - Problem With My “Very Reliable” 15JC-3R/3998L

Hey Billy wow, I and my Wife are both Vietnam vets and have yearly physicals at the VA. I think the worst pain I experienced during this episode was when the Doc was poking around, asking does this hurt? Well he hit a spot I tell you I almost flew off the table! My remaining pain seems to be just where he poked his dam finger. Hope he did not break something inside.

Yes, I have to reduce my fat intake. No more of my favorite treats, Bitch to get old, the body is less forgiving and you have to be cognizant of what you intake.
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Old 02-08-2018, 10:03:27 PM
maineboy maineboy is offline
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Default Re: Onan JC - Problem with My “Very Reliable” 15JC-3R/3998L

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Originally Posted by Leon N. View Post
With all due respect to everyone, I got a feeling he has either a fuel supply problem or a component failed. Could be anything all the way from the gas regulator to a failed spark plug wire or something in between. Can not wait to hear!
Update-
I had a bunch or green box parts, so I’m slowly rebuilding my JC one component at a time.
I checked compression and it showed 80-90psi on all 4 cylinders.
The points weren’t terrible, but they were pitted and gap was huge, so I replaced them and set the gap at .020
The spark on all 4 plugs (grounded to block) seemed weak so I replaced the coil, distributor cap, resistor, and rotor button, but the spark still seems weak?
What else would cause a weak spark ? Any other The battery is very strong
I’m going to borrow or make a manometer to measure the WC at the kn regulator.
I’m also going to check the timing, but I’m still not sure on how this could have changed?
Thanks again for all of the comments and help.
Warm regards,
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  #30  
Old 02-08-2018, 10:11:52 PM
KPack KPack is offline
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Default Re: Onan JC - Problem With My “Very Reliable” 15JC-3R/3998L

Did you use a coil with a resistor or without.
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