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Onan 6.5 NH Running Badly


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  #1  
Old 05-06-2015, 05:27:11 PM
Viking66 Viking66 is offline
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Default Onan 6.5 NH Running Badly

Hi all I am having some trouble with my 6.5 NH at my Camp.

It is a Onan 6.5 NH-3CR 16004P Serial # L833729368

It wants to hunt real badly and then run ok for a few seconds, then hunt. I put up a video here which will show what I mean; http://youtu.be/qF2_IagRr5s

It does this on both Gasoline, and Propane. It started to do this one night and has continued since.

Here is what I have done so far. I cleaned and blew out the Carb, changed Intake Gaskets, New Governor Spring.

Can a leaking Intake cause this to happen? Clean behind the Heads and Valves?

Thanks all

Last edited by Viking66; 05-06-2015 at 10:01:05 PM.
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Old 05-06-2015, 05:57:00 PM
Max Thompson Max Thompson is online now
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Default Re: Onan 6.5 NH Running Badly

Sounds more like loss of ignition spark than fuel mixture (intake leak).

I would eliminate the low oil switch (after making sure the oil level is good), put a spark tester in the leads.

A test light on the + side of the coil will also let you know if the problem is in the low ignition voltage or possibly on the high side of the coil.

Someplace to start anyway.
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Old 05-06-2015, 05:59:27 PM
Sir Thomas Sir Thomas is offline
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Default Re: Onan 6.5 NH Running Badly

Before starting turn the main screw on the carburetor clockwise until closed but not too tight then counter clockwise 1 1/4 turn. Then turn the idle adjustment screw in clockwise till closed and the back out counter clockwise 1 full turn.
Check the length of the governor link. With the engine stopped and tension on the governor spring, the stop on the throttle shaft assembly almost touches the stop on the side of the carburetor. (One more turn of the governor ball joint would allow the throttle shaft stop to touch the
carburetor.) Tighten lock nut.
Check the choke setting.
Start the engine and see if the problem is corrected.
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Old 05-06-2015, 06:02:53 PM
YellowLister YellowLister is offline
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Default Re: Onan 6.5 NH Running Badly

if it runs fine for awhile is not the adjustments.. like max said ignition issue or vacuum leak.. check the points plunger it could be worn unevenly..

the spark tester will show whats going on..
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Old 05-06-2015, 06:11:13 PM
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lokay5 lokay5 is offline
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Default Re: Onan 6.5 NH Running Badly

I've found that hunting is often caused by a lean mixture, and being that it hunts on both gasoline and LP I would suspect an intake air leak, possibly between the two-piece intake manifold halves. A spray bottle of water is a good test tool.
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Old 05-06-2015, 06:29:47 PM
Viking66 Viking66 is offline
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Default Re: Onan 6.5 NH Running Badly

I did check and re-gap the points, but didn't check spark.

I have another Coil to swap out, and I will check the plunger. It just up and started doing it after a good 300 hours of running perfect.

As always, this place is awesome!!!!
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Old 05-06-2015, 06:33:12 PM
Max Thompson Max Thompson is online now
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Default Re: Onan 6.5 NH Running Badly

Quote:
Originally Posted by lokay5 View Post
I've found that hunting is often caused by a lean mixture,
Listening to the video, it is not "hunting", it is trying to die.
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Old 05-06-2015, 06:35:32 PM
MBB MBB is offline
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Default Re: Onan 6.5 NH Running Badly

You can check with carb cleaner around the intake near the gaskets and where the carb sits. If the engine speeds up when spraying those areas you have a leak.
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Old 05-06-2015, 06:49:30 PM
Viking66 Viking66 is offline
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Default Re: Onan 6.5 NH Running Badly

Now that you mention it, it is more like dieing than hunting. Thanks for the better terminology.

I did spray some WD-40 that I had out there, didn't notice a difference. Maybe Carb Cleaner would show it better. I will get some and try that too.

Last edited by Viking66; 05-06-2015 at 06:52:49 PM. Reason: Added info
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Old 05-06-2015, 07:21:24 PM
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Default Re: Onan 6.5 NH Running Badly

Or an unlit propane torch, when you get near the leak the Rpms will pick up. Cheers Dan
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