fuel pump in Kohler CV engine

I have a riding mower with a CV-12 engine. Sometimes it stops as if out of gas. If I remove the gas cap and wait a moment, a stream of bubbles from the fuel line will bubble up through the fuel. Then it will start quickly and run fine.
I don't see what could be getting pumped up with air except the fuel pump. It's two check valves and a diaphragm operated by a nylon lever. The outlet check valve is at the top, so I don't understand how the pump could accumulate air.
Has anyone else run into this problem?
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On 05/21/2014 09:45 PM, J Burns wrote:

Maybe the vent on your gas cap is plugged?
Maybe the fuel pump is going south?
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On Thursday, May 22, 2014 4:41:27 AM UTC-4, Chuck Finley wrote:

That would be my first suspicion too. He could try leaving the cap loose for awhile and see what happens.

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On 5/22/14, 7:55 AM, trader_4 wrote:

grimy outside. WD-40 and degreaser fixed that. I found it clean inside. The valves work freely and the diaphragm looks fine.
I'll go with the gas cap theory because I have no other ideas. I haven't figured out why this would cause cause air to accumulate under pressure in the pump. It must be under pressure if it comes out after I unscrew the tank cap.
After it has sat a couple of says, it takes a lot of cranking to start, as if the tank had sucked the pump dry. There's a catch: I turn the fuel shutoff when I leave it parked.
I squirted some contact cleaner into the vent hole in the cap. I'd love to take it apart. Maybe I can find instructions online.
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Have you looked at this site to see if anything is near you ? http://pure-gas.org/
They list many stations that have ethanol free gas.
I switched to the ethanol free gas a couple of years ago for the small engines and just to be sure I add in some Sta-bil to the gas. Sofar all my small engines start and run fine. It may be over kill, but it only costs a few dollars more per year.
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On 5/22/14, 6:10 PM, Ralph Mowery wrote:

away with it. I thought summer gas was required to have ethanol to reduce emissions.
Actually, it didn't occur to me that ethanol might have softened my valves. My remarks about good gas were in fun. Whenever the price of gas drops, I like to say I'm disappointed that I can't get the good stuff they used to sell. At one time, when gas was red, I liked to stop at Amoco stations to get white gas because my motorcycle seemed to run better. Then I found out that in some parts of the country, Amoco was red and some other brand was white.
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The ethanol gas has been blamed for many engine problems. I have a 5 kw generator and had to clean out the carborator 2 times before swithcing to the EFG. Also it runs smoother when unloaded on the EFG. The ethanol also is bad on some plastic parts, especially the old engines.
I think they have to sell so much ethanol so some stations can get away with having gas without any in it on one grade of gas.
I remember using the Amco white gas in a car I had with a high performace engine about 40 some years ago. It was either that or the Sunoco 260. Everything else sparked knocked.
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