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Retired Willie
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Discussion Starter · #1 ·
I have a mower with a Kohler M18 engine. When I first start the engine it runs good. Smooth with no surging or anything like that. After mowing about 10-15 minutes, the engine shuts down, like it is starved for gas. If I let it sit for a few minutes it will restart, but only with the choke fully closed, and will stay running for 2-3 minutes, again with the choke fully closed. If I open the choke it dies. I can repeat that choke-closed cycle over and over.

If I let the mower set for a period of time, say an hour or so, then the entire cycle described above can be repeated (starts, runs good 10-15 minutes, etc).

I have taken the carb apart multiple times and "cleaned" it, but there is never anything in the jets, etc. The fuel line is clear of dirt, there is a new inline filter in place, and the gas is new. I replaced the fuel pump, just to be certain it was not going bad.

I can't find a plate on the engine shroud, but I think the mower was build in the late 70's or early 80's.

Thanks in advance for any insight you may be able to provide. I am trying to avoid an expensive shop charge if the problem is something relatively easy to fix myself.
 

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Banned
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1,879 Posts
Make sure the fuel tank cap is vented.
 

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246 Posts
Im having the SAME problem, in my case its not the vent, im leaning toward fuel pump becouse if i watch my clear fuel filter when it stalls, it empties of fuel, i think the fuel pump looses its prime. Iv tuned everything up carb, plugs, filter. I have to price a fuel pump.
 

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4K Poster!!!
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Sounds like fuel starvation to me. I'd pull the fuel line off the carb and run it to another container. I'd let it run a quart or more to see if the flow slows or stops. You may have a partially plugged line or tank outlet. This is assuming that you have a gravity feed.
 

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Old Iron......Forever
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3,139 Posts
This probably isn't the problem, but I was working on a Briggs twin opposed, and had it running fine, when all of a sudden it acted like it was out of gas. I could dribble some gas in the throat of the carb and then it'd crank. But then die. I had to take the air filter frame off the carb and the hood off to see what was going on. I decided to fill the the gas tank all the way up, then see if it would run. It did, but then I noticed some gas on the grille coming from a leak, I guessed, at the fuel pump. What I found was that I had a loose gas hose at the connector to the fuel pump. So when the tank was nearly empty or at least below the level of the fuel pump, it was sucking air. I cut off the end of the hose, and replaced it and then tighten the miniature radiator clamp. That fixed it. I went to the trouble of draining the tank back to where it was when the problem showed up, and then tried it. Instantly started. Been good ever since.

Might be something similar.
 

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Retired Willie
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6 Posts
Discussion Starter · #9 ·
I agree it sounds like fuel starvation and had thought about replacing the fuel line from the pump to the tank, but not all the way to the carb. I'll give that a try Monday and see if it helps. I've taken out the fuel pickup line in the tank itself and blown it out to be sure there was no blockage there. I'm thinking about adding a filter to the pickup line, too, to prevent particle pickup in the tank itself, but that seems like overkill, with an inline filter already in place. I'll let you know if a new line solves the problem.
 

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Retired Willie
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6 Posts
Discussion Starter · #10 ·
Well, the fuel line is not the problem. I also drained and cleaned the fuel tank. There were some small pieces of something in the drained gas, but it would have been caught by the inline filter, and it didn't look large enough to block the supply tube.

Checked the linkages and springs in the governor system and they appear to be OK, and readjusted the needle valve just for good measure.

Running out of ideas.
 

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First, I know nothing about Kohler. However, I have seen the flexible pickup line in the tank get so soft that it collapses under suction pressure from the pump and cuts off all fuel to the engine. Far fetched I know but, give it a look. Good luck, I know how frustrating it can be when you cannot figure something out. Thanks to the forum I found my problem and fixed it.
 

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Premium Member
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You could also have a piece of debris sitting in the carburetor inlet above the needle assembly. You won't be able to see it without disassembling the carb. and removing the seat. If you've established good flow to the carburetor, then install a fuel s/o valve, run the engine until it stops, then turn off the valve. Remove the bolt on the bottom of the float bowl, and see how much fuel comes out. If it's empty, you've found the problem.
 

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Retired Willie
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Discussion Starter · #13 ·
Thanks for the advice, rscurtis. :thanku: Apparently I didn't look closely enough when I cleaned the carb the first time. I took it apart again and sure enough there was a tiny speck of dirt in the float needle valve shaft. In fact, at first I didn't even think it was dirt, but when I blew it out it disappeared. I gave the entire carb another cleaning, reassembled everything and mowed for two hours, without it stopping even once.

Thanks to all who responded. The responses were all valuable.

MGB/Willieey
 
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