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I have a 318 with OnanP218 has about 1100 hours. The problem I'm having is after about 20 minutes of mowing the engine starts to lose power and eventually die. When I take the belt off and run the pto it runs fine. I can spin the main deck pulley fine. I have heard many things it could be from mule drive bearings, bad gas, worn pistons dirty carb. Has anyone had this problem or know what it could be. Thanks. Mike


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How long have you had the 318 and do you knows its history? My initial thought is a fuel problem but 20 mins is a long time for that type of problem to show itself. Does it do this every time after it has cooled down?

It might be helpful to go through the 318 checklist.
 

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Discussion Starter #3
I got the mower this winter I don't know much about it's history. I have changed the coil, plugs, oil and filter I have also adjusted the pto clutch. After I let it cool down it will work again for about 20 min maybe less. I may have added to much fuel additive I'm not sure.


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Fuel Additive wouldn't do that consistently after 20 or so minutes. Sounds like a fuel delivery issue. I would have said someting like the coil, but you already changed that. Might check the fuel pump system, maybe the pulse hole is slightly clogged and doesn't pump good when it gets hot.
 

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I got the mower this winter I don't know much about it's history. I have changed the coil, plugs, oil and filter I have also adjusted the pto clutch. After I let it cool down it will work again for about 20 min maybe less. I may have added to much fuel additive I'm not sure.


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In that case I would HIGHLY encourage you to follow that checklist. As for your losing power issue it might be caused by all kinds of things. I am almost certainly that if you follow that list you will fix it. Do you have compression readings on the cylinders?

You may want to start with replacing ALL the fuel lines (10 feet of 1/4 fuel hose, 10 1/4 inch hose clamps, 1 foot of tygon tubing and two new rubber grommets for the tank and a couple cans of brake clean). Don't forget the line from the crankcase to the fuel pump. Also clean the fuel pump while you are at it. After you have replaced the fuel lines then clean the carburetor. Throw up some pictures and we can help you along the way :goodl:
 

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Discussion Starter #6
Would the fuel delivery problem only happen under load. The only reason I ask is because has soon has I turn of the pto it runs fine.


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Discussion Starter #7
No compression readings I was going to try that tonight. What should the compression be?


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Would the fuel delivery problem only happen under load. The only reason I ask is because has soon has I turn of the pto it runs fine.


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It could, under load the tractor is using more fuel which is not there because there is a fuel delivery problem.
 

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I will Start with the fuel delivery and go from there. So if I unhook the line going to the carb after it is hot. There should be a steady flow of fuel. I think I read about 4 oz in30 seconds.


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I will Start with the fuel delivery and go from there. So if I unhook the line going to the carb after it is hot. There should be a steady flow of fuel. I think I read about 4 oz in30 seconds.


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Yes, about the best way to test the pump is to take the plug wires off, take the fuel hose off the pump and measure the flow at the pump. I have a hunch that the line from the pump to the crankcase if cracked and air is getting into the system there.... but that is just a hunch. How full is the gas tank. As you are driving around gas could be sloshing from side to side and the main pick up might be clogged or if you have it on reserve the pickup has flat fallen off......
 

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All good advise but my guess would be worn rings, my 316 did the same thing but it was a bugger to start initally and run 20 min and start slowing down and die.
 

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I have a 318 with OnanP218 has about 1100 hours. The problem I'm having is after about 20 minutes of mowing the engine starts to lose power and eventually die. When I take the belt off and run the pto it runs fine. I can spin the main deck pulley fine. I have heard many things it could be from mule drive bearings, bad gas, worn pistons dirty carb. Has anyone had this problem or know what it could be. Thanks. Mike


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If the PTO components are all turning freely, my first thought is that there is damage in the rear end and filings are plugging up the filter.

Similar symptoms to the engine losing power, but the engine runs fine with no load on the drive.

I had the same thing happen with my MF1655, 20 minutes of work and then loss of drive power. The tiller worked fine.

Drain the rear end and inspect the oil for metal particles.
 

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Discussion Starter #15
That kind of makes sense about the fuel level it's about a quarter of a tank. It looses more power when I turn but I was thinking that was because I putting more load on the engine.


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Sounds to me like it could be a fuel delivery issue so you may want to check that the gas cap is breathing OK (vent should not be plugged). Or it could be lines are sucking air. Have you tested the fuel pump to make sure that it is pumping fuel properly. There is a test that you can do to measure the amount of fuel it pumps, when I get home I'll post it if someone else hasn't already got it up. Also could be the line from the back of the pump to the crankcase has an air leak and that will reduce flow from the pump too!
 

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Thats about how long my 420 would run when the breaker was so corroded it would overheat & trip the breaker, engine would die, let set about 1 minute, fire right back up. replaced breaker & wire ends & all was well.
 

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Discussion Starter #19
I also noticed today my fuel filter is about half full and full of tiny bubbles.


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Are all the screens free of debris, and all the cooling fins on the engine clean ?
Just a thought.
 
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