Kohler engine problems

Anonymous-0 · Dec 20, 2009

Still having problems with the Kohler model CH25, 25 hp engine that has about 400 hours in the Vermeer chipper. It starts and runs for approx one hour until it get hot, then the engine misfires and is unable to run the chipper. Removed both plugs and they look great. Replaced the fuel pump and it ran OK for one day when the ouside temp didn't get above 20 or so degrees F. Originally purchased the machine/engine when it had about 370 hours. Low idle was never really very smooth, but high idle and under load it was OK and we ran it for about 20 hours. Although initially thought we had the problem solved with the new fuel pump, it only lasted for that single day before the hot misfiring problem resurfaced. Again it will start up OK and run loaded for 20 minutes to approximately an hour before it begins to misfire and loose speed. Never really dies, but can't pull much load. Occasionally it might recover for 10 seconds or so, but this recovery is always very brief. Let it cool down for 45 or so minutes and it will run OK again for 15-20 minutes before acting up. Went on the internet and viewed the service manual and apparently this engine has the advanced version of the Capacitive Discharge ignition with SMART-SPARK, or in other words, a timing advance module. I originally thought it was a fuel supply problem, because when the engine started to run rough, applying the choke appeared to help. Now not so sure. Plan is to replace the plugs although they look OK, and also replace the fuel lines which also look OK, because they are relatively cheap fixes before looking at the ignition modules. Hoping someone has some good insight on what is likely the problem or a good approach to determining the problem. Thanks for any help/advice.

Geo-TH,In · Dec 21, 2009

(quoted from post at 06:39:52 12/21/09) Still having problems with the Kohler model CH25, 25 hp engine that has about 400 hours in the Vermeer chipper. It starts and runs for approx one hour until it get hot, then the engine misfires and is unable to run the chipper. Removed both plugs and they look great. Replaced the fuel pump and it ran OK for one day when the ouside temp didn't get above 20 or so degrees F. Originally purchased the machine/engine when it had about 370 hours. Low idle was never really very smooth, but high idle and under load it was OK and we ran it for about 20 hours. Although initially thought we had the problem solved with the new fuel pump, it only lasted for that single day before the hot misfiring problem resurfaced. Again it will start up OK and run loaded for 20 minutes to approximately an hour before it begins to misfire and loose speed. Never really dies, but can't pull much load. Occasionally it might recover for 10 seconds or so, but this recovery is always very brief. Let it cool down for 45 or so minutes and it will run OK again for 15-20 minutes before acting up. Went on the internet and viewed the service manual and apparently this engine has the advanced version of the Capacitive Discharge ignition with SMART-SPARK, or in other words, a timing advance module. I originally thought it was a fuel supply problem, because when the engine started to run rough, applying the choke appeared to help. Now not so sure. Plan is to replace the plugs although they look OK, and also replace the fuel lines which also look OK, because they are relatively cheap fixes before looking at the ignition modules. Hoping someone has some good insight on what is likely the problem or a good approach to determining the problem. Thanks for any help/advice.

James,
I have a ch20 Kohler on a Terramite. It took me 2 years to fix my rich fuel mix. Look on the cover of your engine and you'll find that Kohler has a web sight where you an access a free online shop manual. I think it is kohlerengines.com Look at your plugs for a clue to determine if you have a lean or rich condition. My friend has problems with mice making a nest on top of her single cylinder Kohler. It too would run just fine until it got hot. Then it spits and sputters, loses power and dies. I'm sure that you have checked for wood chips blocking your cooling fins. On my ch20, there are 3 tiny vent holes on the top of the carb and a little dirt got in them and caused my problem. Without taking the carb apart, I just blew them out, Also drilled some holes in the muffler incase it was choked with carbon and it runs great. I have almost 900 hours on it. When all else fails, try reading their shop manual. Good luck, george

jeffalex2 · Dec 21, 2009

Replace the coil and condenser

El Toro · Dec 21, 2009

Pull off the plug wires one at a time when it loses power and and hold it away from the plug about 1/4" to see what the fire to the plugs looks like. If it has a hot spark your ignition is probably ok. Since the engine seem to run ok when you choked the engine it make be starving for fuel. I would remove the gas line at the carburetor and crank the engine with the starter. Hold a clean container beneath the gas line to catch the fuel. Should have a full stream of gas. I would use the 89 octane gas in that engine too. Hal

Mike S · Dec 21, 2009

I had something similar happen to my CC with a Kohler CH15. I did a lot of replacing of parts, new plug, ignition module, rebuilt the carb, etc and it still did it. I finally started pulling the fuel lines apart from the carb back to the gas tank and found that the gas line had trash in it, kept going back to the tank found more trash there. Whe the machine sat for a while, the trash would spread out over the bottom of the tank and the fuel would flow pretty good for a while, then the suction from the pump would gradually start pulling it into the line and slowly stop it up. Once I cleaned all the lines and flushed the tank, no more problems. JMTCW

supergrumpy · Dec 21, 2009

I have same engine but on a Bandit 65, lost low speed this summer and suspect alcohol gas loosened gum buildup in the tank, will pull/clean carb when it warms up outside

when your engine starts to act up, pull plug wires off one at a time, if engine speed drops a lot on either side you have fuel problem, if no speed drop on one or both plugs you have spark issue, I have been warned to replace both ignition modules at same time

as 2nd test, pull air cleaner cover off when engine acts up, spray some carb cleaner into the air filter, if engine revs up you have fuel problem, debris or water in that low tank seems very likely

oldtanker · Dec 21, 2009

Could be simple....what brand of plugs ar you running? I had an Onan twin. After 20 hours on one brand of pugs I had problems. Switched to a different brand and all was well. My dad had the same thing with an AC model CA tractor. The thing would run great with a fresh engine for about 10 hours. Then it would start to act up. Found out that a "major" brand of plugs would go bad in that engine in 10 hours. Different brand and the engine would run many hours without a problem.

Anonymous-0 · Dec 21, 2009

The plugs didn't have a recognizable name. No Bosch, Autolite, A/C or Champion name printed on them. Could be original. Thought they were printed with a CPO or something like that, but would need to look again to be sure. The local small engine dealer wants me to bring one in and sell Champion equivalent after cross-referencing. I've not heard much good about Champion in recent years so probably wouldn't do this and might order originals over the net.

FredinMO · Dec 21, 2009

The smart spark box can fail and cause this,the box changes timing on the engine.Find a good local kohler dealer they should have a smart spark box tester.

Geo-TH,In · Dec 22, 2009

When all else fails, go to kohlerengines.com and down load a free shop manual. I found it very helpful troubling shooting my problem. You may want to remove the engine covers and check for woodchips blocking the cooling fins.

Kruse · Dec 22, 2009

Your gas cap is vented?

Anonymous-0 · Dec 22, 2009

One of the first items we checked, because had a gas cap vent plugging problem on the MH 81 which is hitched to the chipper. Recently the two guys that help seemed to have some problems keeping the tractor running properly when moving the chipper. It had just turned cold so I thought they weren't using the choke correctly and it wasn't a big concern. However the next morning I soon discovered that it wasn't a choke problem when I went for the 81 and chipper. The tractor fired immediately, but only ran for about 3-4 minutes and died. Puzzled about what possibly could be the problem because I had recently filled the tank and was sure the shut-off valve was opened. After it died the second time, decided to check the gas level and could barely turn the cap. After finally getting the cap opened and determining the tank had adequate gas, decided to test the vent. Again went about another 2-3 minutes and it died with the cap tight. Loosened the cap and never had any more problems that day. Later used a wire to unplug the vent.

Anonymous-0 · Dec 22, 2009

Likely the first thing I'll do after installing the new fuel lines and new plugs because it is so readily accessible. Next will be to tackle the ignition modules.

Anonymous-0 · Dec 22, 2009

Already have done this or wouldn't know about the standard ignition and SMART-START engine versions. No doubt very useful and wouldn't want to tackle much without it. However, advice from this forum is light years ahead of the manual's brief trouble shooting guide.

stronics · Dec 24, 2009

When the engine dies or doesn't run right what does the spark look like. Any tinge of red to it? If so probably the module.

Anonymous-0 · Dec 25, 2009

A little concerned to remove the plug wire when it is running and see how far it will spark. The service manual warns about "blowing" the CD module if you don't allow it to discharge. Replaced the fuel lines earlier today and upon removing the inlet side of the fuel filter, I started to see brown stuff dripping out. One of the first things done when we got the machine to replace all the filters and change oils. Although haven't confirmed that fuel tank contamination is the source of the misfire, it certainly is a problem. The brown crud has got to be rust. Unfortunately I had just filled the tank and hate to drain and discard all of the ten or so gallons and don't desire to purchase another $8.00 fuel filter and contaminate it before flushing the tank. I used ether to back flush the filter and got a bunch of crud out. The plan is to let the ether evaporate, reinstall the filter and use as much of the gas as possible before a complete drain/flush. I have sealed a rusty gas tank before and although it works well, hopefully can avoid repeating this labor intensive effort. Definitely need to resolve this issue before going further and hope the planned drain/flush coupled with a new filter cures the problem. As others had already stated, a bad gas supply might be the only problem.

Geo-TH,In · Dec 26, 2009

If you are as cheap as I am, you would drain the gas into a can and use a funnel with coffee filters. To hold the filters in place use clothes pins. May take a few filters. If you are worried, do the same thing when you refill the tank. Hope it works. My guess is that you will need to get the crud out of the cab too. George

Kohler engine problems

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