We Have A 25 Hp Kohler Engine On A Sabre Lawnmower. Before It Quit Running We Had To Run It With The Choke Slightly Out. We Replaced The Fuel Filter Today And I Noticed That There Was No Gas Going To It. There Is About A Half Of A Tank Of Gas In The Mower. I Took An Air Compressor And Blew Back On The Line And Air Was Coming Up Through The Tank. I Know There Is A Possibility Of The Fuel Pump Being Bad, But Won't There Still Be Gas In The Line Going To The Filter? Can Someone Suggest What To Check And Explain How The Fuel Pumps On These Things Work? Thanks For Your Help!!!

so the filters before the pump? what kinda filter is it?

Kohler uses a few kinds of pumps. Some are mounted on one of the valve covers and are pulsed just like a car with action from a valve/tappet. Most are vacuum operated and will have three hose hookups. One will come from the tank, one out to the carb and one to a vacuum source, probably to the valve cover or a fitting on the block somewhere. I've only seen a couple of Sabres because we don't have a Home Depot that sells them.

I think I would pull the hose from the carb and put it in a bottle, turn the engine through to see if the pump is pushing fuel. You may want to gravity feed the engine for a minute to see how it runs without the pump in the line. I assume the gas tank is under the seat somewhere. If the tank happens to be mounted under the dash you could do away with the pump and just gravity feed it.

The partial choke you have been using to get the engine to run points to a blocked main jet in the carb. A weak or failing pump will not really cause this but will cause a running out of gas situation. Running the engine on partial choke will cause extra heat which is not good.

Mike

Mike,
Your correct on the pump. It does have 3 lines and it seems to be vacuum. I was wondering if there was anyway to verify the pump had the correct vacuum or if there is a way to determine for sure the pump has failed. I took the cover off the pump and it looks like the diaphram is intact. What I didn't understand is the last time I changed the fuel filter there was gas up to it from the tank line. Right now the line is off and there is no fuel running out of the tank line and I know there is plenty of gas for it to gravity feed. Is there some type of filter in the bottom of these tanks?? Like I stated in my orginal posting, I blew back through the tank line and air was coming back up into the tank. See, I'm working on this for my father, and I would like to definately identify the problem before I start throwing parts at it. Any help would be appreciated....Thanks

Bugman,
It is a clear plastic filter with a paper element.

oooh, those paper filters, was it original equipment? or a non oem one? i've had one of those paper filters, they don't flow good. oh and filter in the tank, some have a mesh screen in em, where it hooks up, and can get clogged.

With the gas line lower than the tank and removed from the pump you should have free flow. I don't think gas can gravity flow through a healthy pump. Try loosening the gas cap.Thats really a shot in the dark but if the gas cap vent has failed gas can't flow out. You have got to get gas gravity flowing from the tank somehow to move ahead with this problem. Once you have this done put the hose back on the pump. Pull the hose that goes into the carb and put it in something that will catch the gas. Try cranking the engine over and if all things were in order it should pump fuel. I really doubt you have a vacuum problem as in lack of. About the only way it could be short would be if it lost a rod or something. If you really want to check the vacuum you will need a gauge and hook it were the pump gets its vacuum. I'm not certain about the exact lbs. it needs, something over a 3-4 lbs. would probably be fine. To do that you would have to gravity feed the engine like I mentioned earlier. That needs to happen anyway to verify that the engine itself is fine. Just get an old tank from anything, hook it to the carb inlet, hold the tank over the engine and fire it up. If it runs fine you almost certainly have plenty of vacuum.

You say the pump has a cover that comes off. That means that there must be kits available for it and it couldn't cost much to rule out a bad diaphragm.

Mike