I wasn't sure if this went here or in the Garage/Workshop Forum so if it needs moving, feel free.

I have a six year old Craftsman 42" riding mower/lawn tractor with the Kohler 16 HP motor. It's the motor with the pressurized oil system and automotive style filter. If I had to guess I'd say it has about 150-200 operating hours on it.

It starts and runs perfectly for 45 minutes or so - long enough to do about 15,000 s.f. in my back yard. When I move to the front it starts to miss, cut out some and die. At first it would only do it going up the slopes but now it is doing it more often and today it was quitting completely even on level ground.

After a couple minutes it would restart full choke but would die out once I pulled the throttle/choke back to idle or wide open (no choke).

When it first started doing it I thought it might be low oil but the level was fine. I changed the oil and filter and the oil level is right. I also recently changed all the filters and cleaned the carb. It sounds like it is being fuel starved but I'm also wondering about faulty ignition or perhaps the low-oil switch is killing it.

Any suggestions where to start?

Thanks.

 

Most likely a fuel pump diaphragm. Had the same problem myself.

 

Fuel pump or even a vent problem. Is the cap vented?

 

Would the fuel pump be an integral part of the carb or is there a separate fuel pump? Best I can tell the fuel system is strictly gravity fed.

And the vent problem you suggest, are you talking about the fuel tank being vented? If I understand you right, it sounds like I could just open the tank when the problem is occurring to relieve vacuum on the system?

Thanks

 

I had a engine just do this to me. The vent on the fuel cap became clogged. The engine would run for a while (20-30 min) and suddenly lose power, stumble, and shut off. I could get it running on full choke and at idle. When I opened the choke and gave more throttle it would shut off. I opened the gas cap to see if I had run out of fuel and swoosh!!!! The fuel system had created a vacuum due to a clogged cap vent.

Some systems are venter and some are not. An engine of that size, I would think would have a small square fuel pump. They are usually about 1.5" square mounted between the tank and the carb.

200 hours is pretty low to be having fuel pump issues.

One last thing that pops into my mind is water in the fuel. Iso alcohol would take care of that.

 

Just had a customer whose fuel cap was vented with a small pin hole in the top. Exact same symptoms. The guts of the cap came apart easy - cleaned it out and no problems since.
If, when it starts to stutter, you can get temporary relief by choking the engine, it is definitely a fuel issue.
Briggs fuel pumps are mounted on the side of the engine. The fuel line runs right to it then another to the carb. There will also be a crankcase vacuum hose connected to breather. If you have a pump, you can hardly miss seeing it. If it is a gravity feed only, the odds of the fuel tank vacuum being a problem are increased.
Your symptoms are completely consistent with that of a clogged vent in the fuel cap.
Just loosen the cap enough to let air in to confirm, then disassemble the cap and clean out the vent mechanism.

 

Kohler engines use two different kinds of fuel pumps. They are usually both in the same general area. One is bolted right to the valve cover, and it is actuated by the valve train. It will have two lines in it, one from the tank one to the carb. The other kind is usually bolted near the valve cover, and it has 3 lines, one from the tank, one to the carb, and one to the engine crank case.

 

Great information, gentlemen. I wasn't thinking fuel pump and never would have thought gas tank vent. So, even though I cut the grass for the last time yesterday I guess I'll have to find some excuse to run the mower for a while. Maybe mulch some leaves or dethatch or something....

I'll let you all know. I'll start with gas cap and worry about the fuel pump if that doesn't work.

Thanks again.

 

DOH!!!
Sorry I didn't read carefully enough to see it had a Kohler on it.
My bad.
Let us know how you make out with it.

 

Yeah the vent thing sounds like a good bet...

I bought a small outboard off a guy a bunch of years ago that he claimed never ran right for him - it would run for awhile then act like it ran out of gas. He said he'd pull the cap and check - plenty of gas... then (of course!) it would start and run fine for a while.

Bought it cheap, and played with it for a short while.. the fix turned out to be to open the little vent on the cap (yes, the same cap he was taking off to check the fuel level) when you wanted to run the motor...

 

sounds like a fuel issue to me, check teh tank for water or debris

 

im in the lawn business and have several kohler engines. check the fuel filter. things on these engines dont just start to go over time. great quality motor.

 

at the price that used mowers are bringin now days id parkit out by the road and buy a new one! or check the feul pump,coil,ignition,feul filter and replace as needed

 

I took the gas cap off yesterday and gave it a good cleaning with carb cleaner. Gently poked a wire into the vent hole and then blew some air through it at about 5 PSI. There was definitely air getting through under low pressure so it should flow under an equal amount of vacuum.

I changed the fuel filter about the time this started happening. I took the original equipment filter off and put an automotive filter on it - a spare from my VW bug. It is see through and I know it is flowing well. I was thinking that possibly this filter would be too restrictive since it is used on the pressure side of the fuel pump in the VW but with the gas line off the engine of the mower, gas flows freely.

Now, as soon as we have a sunny day (been wet and dreary for five days now), I'll pull her out and start shredding the last ofthe leaves covering my lawn.

 

BULLFROG just hauls ***. The deck is a problem.