kohler engine acts like its starving for gas intermittantly

[ampsucker]

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

 

[oldnslo]

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

 

[crusty 1]

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.

 

[Denwa]

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

 

[ampsucker]

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

 

[ampsucker]

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

 

[oldnslo]

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

 

[psj12]

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.

 

[ampsucker]

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

 

[oldnslo]

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

 

[ampsucker]

i'm curious if someone can explain to me how the new "electronic" needle and seat works. i have taken the bowl off when cleaning the carb. it appears the flow of gas is controlled by an electrically actuated plunger instead of the old style needle/seat/float that i am familiar with. these seemed to show up about the time CARB compliance started and the EPA was mandating cleaner engines.

i'm wondering what actuates this device and what the failure mode is.

i'm wondering if it could spontaneously shut off the flow of gas into the carb for a few seconds of if a spring internally might be broken or loose.

i think it is only sold as part of the carb so that might mean a new carb anyway, but i would still like to try to understand how these new fangled things work ;-)

amp

 

[oldnslo]

i'm curious if someone can explain to me how the new "electronic" needle and seat works. i have taken the bowl off when cleaning the carb. it appears the flow of gas is controlled by an electrically actuated plunger instead of the old style needle/seat/float that i am familiar with. these seemed to show up about the time CARB compliance started and the EPA was mandating cleaner engines.

i'm wondering what actuates this device and what the failure mode is.

i'm wondering if it could spontaneously shut off the flow of gas into the carb for a few seconds of if a spring internally might be broken or loose.

i think it is only sold as part of the carb so that might mean a new carb anyway, but i would still like to try to understand how these new fangled things work ;-)

amp

Amp,
I am 99% sure these are the "Safety" shut off valves on the carbs and do not do any metering. Yes it is possible you are loosing the signal to it. Would require a test light or meter to check voltage. I have never heard of one of these failing but... being man made it sure is possible. I would think that a Kohler dealer would sell them as a seperate item. JD may not.

JD MAY have requested a special engine model number from Kohler so that it makes buying parts from any one but JD difficult. I know JD had Kawasaki do this to their motors used on JD equipment.

good luck

Roy

 

[jhwentworth]

"i'm curious if someone can explain to me how the new "electronic" needle and seat works."

That gadget (electric solenoid)at the base of the carb bowl isn't a needle and seat. It's purpose is to reduce the risk of backfires when the engine is shut off. When the key is turned off the solenoid blocks the flow of fuel to the main jet. You should hear the solenoid "click" as the ignition is cycled on and off.

These solenoids do fail, or, more likely, the wiring or connections to the solenoid. I worked on a riding mower today that had a faulty connector on the wire between the solenoid and the switch that caused the engine to intermittenty starve for fuel. When you wiggled the connector you could hear the solenoid clicking.

Some folks fix this problem by removing the solenoid and replacing it with a simple bowl bolt. That also fixes the problem of a dead battery if you leave the key on. The solenoid draws enough juice to kill a battery in 2-3 days.

 

[BXinNH]

I have a 16hp version of your tractor. I added a fuel filter to the line a few years ago (it did not have one) and it started having very similar symptoms to what you are describing. I ended up cutting a few inches out of my fuel line to compensate for the length of the filter. The problem went away. Some how the added length/change in elevation was affecting fuel flow under certain conditions.

Matt.

 

[ampsucker]

thanks for the all ideas and information! next time i mow, i'll try out these new ideas and post back.

if i don't post for a few days it's because the wife is due to have our second baby within the week, so there will be higher priorities than mowing!

amp

 

[brokenot]

I have a 16hp version of your tractor. I added a fuel filter to the line a few years ago (it did not have one) and it started having very similar symptoms to what you are describing.

You'd be amazed at how many problems like this have been created by adding/swapping the original inline fuel filter for one that "fits" or "looks the same". I'm all for saving some $$ by using aftermarket stuff, but only if it's truly equivalent to the OEM part.

The biggest caveat with using aftermarket inline fuel filters on small engines like this, is that many of them simply are not designed to work with the fuel pumps that many small engines have. If your engine has one of the OEM pumps that operates off of the pulses from the crankcase, it's best to spend a few extra dollars and buy the original recommended filter instead of installing a generic inline filter from the parts store.

We have three Toro Dingo walk-behind skidsteers in the rental fleet with 20-25 hp Kohlers. They have all acted similar to the issue the OP is describing after someone replaced the original inline filter with a generic one from Napa or Carquest. Those small fuel pumps simply do not produce as much "oomph" as a larger mechanical or electric pump like a car or light truck has. You think you're doing the engine a favor by staying on top of the maintenance stuff, (and even more so by adding a larger filter that looks better), but you often wind up causing problems when the fuel pump can't suck the gas through the element

Probably the most common Kohler fuel filter number in use on these engines is a part # 24-050-02. My garden tractor with a 20 hp Kohler takes that one, and the Dingos do as well. The parts manuals for the machines even list that number.....the machine manufacturers don't even try to sell their *own* part.

I wouldn't bypass or eliminate the carburetor solenoid. They're easy to diagnose, and inexpensive to replace if, (unlikely), they go bad.

 

[mbob]

Hi,

I am trying to diagnose a very similar problem. My Kohler is 4 years old and is acting like its starving for gas after about 40 minutes. If I disengage the blades and wait a bit it seems to recover for a short time again. The fuel filter is clear and only has a little gas on the bottom, barely any.

This spring I changed the fuel filter and plug. Thinking it may be a bad plug I just changed that again and it was not the issue. I am getting ready to find another fuel filter but I used the recommended Kohler part so it most likely is not the issue.

I would gladly pay to have it repaired but I do not have a way to transport it and there are no in home repair availible to my area. Are there any other "dummy proof" things I can try?

 

[ampsucker]

ok, check this out.

i had occassion to use the mower heavily this week. before starting, i decided to unhook the solenoid wire just to see what would happen. if working correctly, my understanding is this action of powering down the solenoid magnet should allow the spring to push the needle into the carb orifice stopping gas flow and the engine should not start at all. if this is incorrect, someone please advise....

well, imagine my surprise as the engine ran flawlessly for about 5 hours of mowing!

i know.... that is bizarre, right?

i guess that points to a defective solenoid but failing in an odd way intermittantly. i imagine the needle just kind of floating around in the end of the assembly periodically plugging the orifice when the governor demanded more fuel. as for why it doesn't do this when the wire is unplugged beats the heck out of me.

well, whatever works. it doesn't leak and the engine runs great so i'm leaving it unplugged and mowing like a fiend....

hope that helps somebody.... ;-)

 

[ampsucker]

i will also add that i am running an aftermarket fuel filter (hastings i believe?) and that doesn't seem to have an effect on the engine performance in any way.

 

[junque2k2]

Good to know I'm not alone, apparently this is a common symptom with Kohlers.. aside from those caused by bad fuel & filters. I have a 6 month old Kohler Pro CV492S 18hp and it starts and runs fine for 30-45 minutes then begins to stall like it's has fuel starvation or out of gas. Wait a while and it will run again which makes it sound like a temperature related electrical problem. The carb fuel bowl solenoid shuts off fuel flow to the carb when the key is off and prevents dieseling too.. might also be tripped by a safety tip over sensor to kill the engine. I read on other forums that the solenoid can become corroded by water in the bowl and cause trouble but I found a repair tech had already disabled the solenoid by cutting off center pin on mine.. For another shot to find a cure I used a can of dust off to chill the ignition module on the chance it was hot (even though it was cool to touch, apparently some designs get warm enough to require a heatsink). One forum suggested the fuel line was getting hot and causing the fuel to vaporize but I don't think it's the problem here. I have good fuel flow from the tank to the bowl with a new 60 micron filter & new gas. Guess I'll keep reading.. the thing farts when I shut it off too.