kohler engine acts like its starving for gas intermittantly

   / kohler engine acts like its starving for gas intermittantly #1  

ampsucker

Platinum Member
Joined
Dec 6, 2007
Messages
574
Location
Southeast Kansas
Tractor
BX24
howdy!

i have a 17.5 kohler single cylinder 4-stroke on one of the Scott's/Deere lawn mowers with about 650 hours on it. it runs great most of the time but under a heavy load acts like it's starving for gas every 5-10 minutes of mowing. i'll hit a heavy spot of grass and when the governor requests more fuel from the carb, it stumbles and almost dies. if i stop forward motion and drop the throttle down about half, the engine will catch up and then run fine again up at full throttle for 5-10 minutes.

i have replaced the fuel filter and fuel pump and cleaned the carb. i also put on a new governor rod retention clip ordered new from deere. the fuel tank seems clean and doesn't act like there is a vacuum or pressure build up when i take off the fill lid.

a new carb is about 150 bucks. i may do this next as i feel i'm running out of options and need the mower to work this season. i don't know much about these modern carbs. this particular one has a wire with a plunger device mounted in the bowl of the carb which takes the place of the older style needle and seat. there is one adjustment needle on the front of the carb body which i believe is low speed or idle adjustment.

anybody have any ideas or common failure modes on this engine? i'll have to order a new carb soon, if i can't fix this one.

any thoughts much appreciated.

amp
 
   / kohler engine acts like its starving for gas intermittantly #2  
Are you sure it's fuel and not ignition related? My Old JD 112 with a Kohler single did the same thing. Ended up being the ignitiol coil getting warm and failing. Mine is and old points and condesor with coil. Yours may be electronic ignition but they can do some strange things also.

Try pulling the plug and check for good spark when it is hot and failing. Also try a new spark plug. Have seen a couple of them fail when warm also.

Diagnosing intermittant failures is a PITA.

Good luck

Roy
 
   / kohler engine acts like its starving for gas intermittantly #3  
ampsucker, my old 216 deere did like it sounds yours is doing and after a bunch of bs turned out to be crud in fuel tank getting sucked off bottum of tanl restickting fuel to the line.
 
   / kohler engine acts like its starving for gas intermittantly #4  
howdy!

17.5 kohler single cylinder 4-stroke..... i'll hit a heavy spot of grass and when the governor requests more fuel from the carb, it stumbles and almost dies. if i stop forward motion and drop the throttle down about half, the engine will catch up and then run fine again.... the fuel tank seems clean and doesn't act like there is a vacuum or pressure build up when i take off the fill lid.

amp

Try dismantling and cleaning the air passages in the fuel cap. Sounds like you may be pulling a bit of a vacuum under very heavy load. This is not uncommon with older motorcycles.

As a test, next time it happens immediately loosen the fuel cap if you can safely do so, which isn't likely.

Let us know,
Dennis
 
   / kohler engine acts like its starving for gas intermittantly
  • Thread Starter
#5  
thanks guys. i'll be mowing this afternoon and will try suggested ideas.

the reason i didn't think it was ignition/electrical is because the engine immediately recovers if i pull down the throttle. it's like it starves out of gas or air and then as soon as the rpms or governer demand is lowered, it runs fine and you can raise the throttle again.

i did actually have an old dead leaf in the fuel tank but pulled that out when this first started happening. i thought it might be sucking up against the fuel line intake and stopping the flow of gas. i can see down into the tank and it looks pretty clean now. nothing large enough to block the fuel line. it's a clear plastic tank and you can look right at the bottom through the fill hole and see the fuel line pickup area.

i'll try a new spark plug and clean air filter and check the other things you guys mentioned and get back with you after running it a bit.


thanks,
amp
 
   / kohler engine acts like its starving for gas intermittantly
  • Thread Starter
#6  
ok, ran it a couple of hours yesterday.

i put in a new spark plug. this did not seem to affect it. in fact, it seems more random today than ever. sometimes it would sputter and stumble even with a light load or hardly any grass to cut. a couple of times when it started to die, i pulled the gas cap off the tank. there did not seem to be any vacuum and i could easily blow through the vent hole in the cap so it isn't plugged. (note to self: keep a mint handy when blowing through a gas cap vent. that taste really sticks around.)

i'm starting to think maybe it IS an iginition component failing when it gets hot. the first failure happened about 5-10 minutes into the mowing cycle. i had made it almost through my second trip around a typical residential 10,000 square foot yard. from then on, every 3-4 loops and it would stumble. take the load off, drop the throttle, engine recovers and is fine again for another 5-10 minutes.

sure acts like a plugged fuel line or fuel delivery problem, though. very strange.

please keep the ideas coming if you can think if anything else. if we can't figure it out, i guess i'll be pricing ignition components at deere pretty soon. they are probably less expensive than a new carb.

amp
 
   / kohler engine acts like its starving for gas intermittantly #7  
Do you have a manual choke on your machine? If yes when it acts up what happens if you pull the choke out part way. Might give another indication of fuel or spark issue.

How old of an engine is it? Does it have the seperate points, condensor and coil or is it electronic ignition? Kohler has a website that will give you a parts breakdown for engine. Your will need the model and spec number though.

Been awhile since I had to but a Kohler ignition but would guesstimate in the $60 - $70 range.

NOTE: What you are describing is exactly how my old Kohler acted with the bad coil. Would idle fine but would not rev up.

Good luck

Roy
 
   / kohler engine acts like its starving for gas intermittantly #8  
Just had a similar problem on my son's ZT mower. Some small bugs got in the gas tank and died. They were stuck in the brass, right angle fuel fitting on the bottom of the tank. You couldn't see them but they flew out when compressed air was shot through it. I suggest you blow through all your fuel lines and fittings to remove debris.
 
   / kohler engine acts like its starving for gas intermittantly
  • Thread Starter
#9  
the choke IS manual. it is the type operated by pushing the throttle PAST the normal full throttle position. i've inspected the linkage and it seems to be operating normally. one of my first thoughts was the choke was falling closed periodically and causing the stumbling.

i will try intentionally choking it next time i run it and the problem occurs to see what type of effect it has.

oldnslo, mine revs up fine and runs at full throttle for 5-10 minutes before chocking out for 20-30 seconds. then runs fine again.

amp
 
   / kohler engine acts like its starving for gas intermittantly #10  
occurs to see what type of effect it has.

oldnslo, mine revs up fine and runs at full throttle for 5-10 minutes before chocking out for 20-30 seconds. then runs fine again.

amp

Mine ran fine until warm just like yours, difference is it would typically not run good again until it cooled off.

You may want to blow out the fuel lines jsut to make sure there is not some obstacle plugging them. Might even consider replacing them if they are readily accesable. Cheaper than carb or ignition and removes another variable from the system. Hoses occasionally have the "inner tube" seperate from the housing. This inner tube can colapse or start to degrade and potentially block fuel flow. Rare but it does happen.

Roy
 
 
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