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Premium Member
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Discussion Starter #1
The Onan p218G in my 317 has developed a peculiar problem. It starts up and runs smooth as silk. After about 20 minutes of use it starts surging. It's subtle at WOT but there. At idle it's more obvious, but the tractor does not stall out. The tractor got a new air filter and oil/filter change with SAE30 dino oil when I got it in June. Any thoughts?

Also, it seems to creep more after about twenty minutes too, is that just the hydro fluid getting warm?

EDIT: One test I just thought of, I haven't opened the gas cap to vent when it starts surging, I'll have to give that a try.

The picture is just 'cause:

 

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The Magnificent
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20,952 Posts
Did you run through the infinity point checklist yet? Sounds to be a fuel delivery issue for sure.
 

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THE TRACTOR HUNTER
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2,225 Posts
Fuel for sure. The picture above helped me diagnose your issue....:howdy:
 

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383 Posts
My 316 did that for a little bit when I first brought it home in July. I adjusted my mixture (which turned out to be WAY out) and the surging went away. Glad it wasn't the governor acting up. I'd look at fuel issues too- easiest ones to fix. ;)
 

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Super Moderator
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33,676 Posts
Surging Onan could be a number of issues: Leak on intake manifold, fuel pump dirty, and/or air leaking in fuel lines. Simple test is to run a line to carb and let fuel gravity feed and see if it still does it. If it does then likely the mixture or manifold leak, if not then fuel pump or air in lines or with a 317 the strainer on the fuel line at the bottom of the tank getting clogged.
 

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Premium Member
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799 Posts
Make sure your air filter is clean and then reset carb fuel mixture. With season change and normal wear and tear they go out of adjustment. It is also quick and cheap. If the problems still persists then go looking for other things. No sense opening a can of worms if there is no fish to be found.
 

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Premium Member
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9,785 Posts
Discussion Starter #8
Make sure your air filter is clean and then reset carb fuel mixture. With season change and normal wear and tear they go out of adjustment. It is also quick and cheap. If the problems still persists then go looking for other things. No sense opening a can of worms if there is no fish to be found.
That last part is always good advice! This is my first Onan. What screw(s) am I messing with on the carb? If anyone has pictures that would be great!
 

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Three of my friends
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Here is a carb diagram and the adjustment screw is#13,you will have to remove the aircleaner and you can access it,while you have the ac off remove the top of the carb and clean out the idle jet along with the carb inside.There have been a lot of Onans this year with surgering and most of the time is on idle but have a look at this jet # 7,there MUST be a hole completly through.
 

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