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gas in the oil of a Kohler engine

Posted by oneleggedman (My Page) on
Sat, Sep 20, 08 at 14:01

I have a 5-6 yr old Scott's mower built by John Deere. It has a Kohler Command 16hp electric start engine. It has been reasonably well maintained with regular oil/filter/plug changes season to season. I recently checked the oil and was getting a low reading. I thought this was odd as typically the oil has never run low during a season. None the less I added just over a quart of oil and it still read at the same low spot on the stick. I didn't want to add more oil for fear of overfilling. I started the engine and after about a minute or so got a thick cloud of bluish-white smoke, it started to clear, but after a couple of minutes the engine shut itself down. I restarted it again, got another cloud of bluish-white smoke, and another stall.I did this about 3 times with the same results. I suspected that I had inadvertently over filled the oil so I started to drain some out. When I did I found that I had a mix of gas and oil draining out. I drained about two quarts of gas/oil mix and think I may have been draining the gas tank through the oil drain. Did I blow the head gasket? or is it possible that the float in the carburetor is stuck? Any help would be greatly appreciated!!


Follow-Up Postings:

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RE: gas in the oil of a Kohler engine

The carb is the culprit.
Either a stuck float (relatively rare IMO) or the needle & seat has a piece of crud preventing it from sealing.
You'll need to remove the needle & flush the crud out.


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RE: gas in the oil of a Kohler engine

And after you get the overflowing carb problem resolved, install (and use) an inline fuel shutoff valve to prevent the carb from filling your engine with gasoline if the carb ever does this in the future.


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RE: gas in the oil of a Kohler engine

IMO Gunk in the bowl, without full fuel system clean-up it will happen again most likely.

Fuel system clean up starts in the fuel tank, drain it (you most likely be amazed what you find in there), remove it, clean the inside out (swabing, pressure washing, rocks and gas, what ever but make sure it pristine clean, flush the fuel lines and inspect them for cracks or rot, replace any questionable hoses. replace the filter, flush the fuel pump to clean it out (if it has one), (fuel pumps on kohler is another way fuel can get into the crank case, just like fuel pumps on old chevies or ford the diaphram my leak/crack and pump gas into the crankcase). Remove the carb bowl (and o-ring Carb cleaner may cause it to swell and maybe pinched upon reinstallation) and clean it out.

I would also wash the carb area under the bowl where the float is with carb cleaner, wash the fuel shut-off valve and test it using a 12V source. lub the carb. bowl o-ring with vasoline so it won't get pinched, install the bowl holding while starting the fuel shut-off soloniod tighten it hand tight while watching the bowl to o-ring seat for pinching. use a wrench put final torque on the shut-off valve noting how tight it was when you removed it.

If you plan on keeping the LT for awhile regular routine maintenance is required to keep it running in tip top shape. Fuel system clean up IMO is required every 3 or 4 years.

Over filling the crank case can cause internal engine damage including blown head gaskets. Most likely it push some of the seals out and may of push the head gasket out also. If you got lucky you will probably see alot more oil leaks at the minimum IMO. remember this is only my opinion other will say Baabaaaabbbaaa it not required, but they haven't experienced fuel related problems YET. then, again the carb. may have to be overhauled, but atleast the fuel system will be clean?!? The oil changing nerd!!! Rc


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RE: gas in the oil of a Kohler engine

Gas infiltrating crankcase
I have a Kohler Command Model CH 20S/ Spec# 64501/ date of manufacture 2001

I have replaced float and valve. Changed oil and filter. Engine ran great. However, after approximately five minutes, began producing white/blue smoke. Removed oil down to app. 1 quart (holds 1.9qt.) such that oil stick showed oil at a little over "low" mark.

Ran great, for about five minutes and, again, white-blue smoke

Drained crankcase of app. 2 plus quarts of what I would estimate to be a 1:1 gas/oil mixture.

Have removed carburetor, no leaking gas observed (gravity feed gas line).

Removed valve cover where mechanical fuel pump is located. Observed rust on both push rods, much more pronounced on the rod the lifts the rocker arm that operates the fuel pump. Also, some rust on the one-way valve to carburetor. (Note: it was reported by cousin who had borrowed this piece of equipment that there was water in the crankcase and we puzzled over how that could have occurred.)

Now, my best guess is there is a leak in the fuel pump, thus, explaining entry of gas and water (later via condensation within gas tank?) into crankcase and rust at top of push rods.

Do I replace the valve cover/mechanical fuel pump, to eliminate the gas into crankcase problem?

Do I replace the push rods, or, just clean them? To remove push rods, will I need a rebuild kit, i.e. does this involve tearing engine down?

Thank you,

Mike Gamble

Dothan, Alabama"


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RE: gas in the oil of a Kohler engine

i have a kohler 16 on a john deere im not an expert but i can work on things mine was getting gas in oil after a complete fuel system service i decided to look elsewhere well the fuel pump on this particular engine is mechanical and there is the problem diaphram was torn and getting gas in oil 41.00 at the deere store it runs great now. check and if its getting it in there while its running it cant be the carb how could it? think about it guys.it would put out the fire.


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RE: gas in the oil of a Kohler engine

Onelegged, I registered for this forum so that I could thank you and the other members that responded to your post. I have a used John Deere LT 133 and just experienced the same symptoms you described in your post. When I saw your explanation of what had happened it was almost word for word what happened to my lawn tractor.

I started the tractor up and noticed that it was running rough so I checked the oil and saw that it was low. I added a little over a quart of oil and the oil level still did not rise much.

I started the tractor and got the same huge white ball of smoke and then it would run for about 2 minutes and cut off. At first I figured that I might have overfilled the crank case so I tried draining the oil and a mess of oil and gas poured out.

Bottom line, I thought I might have ruined the engine and thought I�d check out prices for a new 13 Hp. Kohler. While I was looking I thought I�d see if anyone else had had similar problems with their Kohler engines well, low and behold one of the posts I came across was yours.

When I saw some of the responses I was so relieved. Based on responses to your post I have found that my fuel pump was the culprit, the diaphragm had a tear in it that was leaking fuel into the crankcase.

I was so impressed that I promised myself that I would post to tell you how thankful I am for your post and share how it helped me. Thank you and those who offered their expert advice so very much!


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RE: gas in the oil of a Kohler engine

Just had to post to thank everyone for their great answers on the gas in oil problem with my Scott's ridding mower. I know it was an old question and a old post but I just wanted to say thank you !!!!! You guys here saved me probably a fortune in a repair bill and it was to me an easy fix. It was the carburetor that was a little dirty so I guess something was sticking and letting the fuel just keep flowing into the motor. When I tried to start it for the first time this season it smoked with white smoke like crazy. I tried to start it again and the starter would barely crank because it was so full of fuel and oil. I ended up removing the carb and cleaning it. I replaced that and drained all the fuel/oil mix out of the oil drain and replaced with new oil. Started it up and it smoked for a little while but not like before and then after about 5 min. Of running it stopped smoking and ran fine. Good thing too because my grass was almost knee high. Thank you again for your solutions. They helped me out a lot!!!!!!!! Keep this forum going!!!!!


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RE: gas in the oil of a Kohler engine

On the Kohler Command 16 there is no fuel pump, just gravity feed. I can see what looks like a float bowl just below where the fuel line connects. How do I access the needle and seat mentioned above by Bill_Kapaun? There is what I think is a fuel shut off solenoid attached to the bottom of the float bowl. How is the bowl removed? Thanks for any help.


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RE: gas in the oil of a Kohler engine

somewhere on that engine there will be a plate/decal or numbers stamped into the cowling sheet metal giving you the engine model #, type#, S/N and DOM.
Take info - go to engine mfgr's website, download service manual and parts list for that particular engine. You will find all your answers there.


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RE: gas in the oil of a Kohler engine

I have a 24 year old Deere STX-38 with a Kohler CV 12.5 - 1215 engine. I check the oil EVERY time before I use it, but last time, the dipstick was pristine, as it would be after an oil change. I couldn't discern a fill-level, but a sheen of oil was present. I have been noticing an oil leak deposit below the engine for 6 months or so, but not a noticeable lack of oil on dipstick. I do have to add some every once in a while, but, considering age of mower, was not duly alarmed. This time, after using a battery charger on "engine start", it started immediately, then ran roughly, emitting blue or black smoke, as one would if it had been over-choked. I let it smooth itself out, and all seemed OK until the engine began to stumble badly, and emit an immense cloud of WHITE smoke. I shut it down right away, thinking that the engine would have seized-up. The following day, it started immediately without the battery charger, then began to stumble and emit blue smoke, so I shut it down again. Dipstick smells strongly of gasoline, and air filter pre-cleaner is quite oily. l have read that crankcase breather could be cause of this, and engine usually backfires when being shut down. Is this a Harry Home-owner type of repair, or have I been condemned to the repair shop? Thanks, everybody, for your patience and advice..


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RE: gas in the oil of a Kohler engine

pull the dipstick again as if you were going to check oil level and smell the stick's residual oil... if you smell raw fuel, immediately drain/replace crankcase oil and filter. Raw fuel in oil will cease lubricating your engine, leading to early life failure.
If your machine is set up with a gravity feed fuel tank, purchase and install a manual fuel shutoff valve between the tank and the carb.
M/W, find source of raw fuel leak into crankcase - usually carb float valve or faulty fuel pump - repair before operating engine.
Renew air breather elements as needed.


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RE: gas in the oil of a Kohler engine

Thanks very much, rcbe6. Will do first thing tomorrow. There is a fuel shut-off valve between tank and carb already, but I'll have to find out just where and what a float valve is. I know it can be found by removing the metal bowl, and I recognize the float itself, but haven't a clue what a float VALVE looks like, and ditto its location....

Now, what could cause the oil LEAK ?


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RE: gas in the oil of a Kohler engine

***" There is a fuel shut-off valve between tank and carb already"***.
Well, if there is, you need to train yourself to shut off that manually operated valve at all times.......except when you are actually running the engine.
You should go to the Kohler website and download a free copy of the service manual for this engine. It will help you decide if you want to go digging in the carburetor, and show you how if you decide to do that.
If the gasoline in oil condition has persisted for a while, that may be aggravating the "oil leak" deposit you see. Thinned oil leaks out easier than full bodied oil and gasoline inside the crankcase actually builds a fair amount of pressure (to force oil out) in the crankcase when the gasoline boils off as the engine warms up.
Let's get the gas leakage issue resolved first and then see if you really have an oil leak.


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RE: gas in the oil of a Kohler engine

Mownie, thanks for your prompt response to my plight, and for your kindness and patience. I just hit 77 this week, and, despite being a bit timid about taking apart a carburetor, I am quite handy with things mechanical. I've just seen it done via u-tube, and it looks fairly easy. It seems that the appropriate kit contains not much more than a few gaskets and a replacement rubber-tipped needle valve, so all else would consist of a few simple hand tools and a can or carb cleaner, no?
But, first things first: today, I will close fuel shut-off valve, than drain and replace oil, and finally, install new air-cleaner and foam pre-cleaner ( I have two new spares). Again, thank you, thank you, and thank you.


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RE: gas in the oil of a Kohler engine

Phil, Happy Birthday and congratulations on your achievement.
I will recommend that you attack the carb disassembly work inside the confines of a large baking pan or cookie sheet that has some sides on it.
The pan will keep all the screws and stuff corralled nicely.
Be patient and if you have a digital camera, shoot lots of pictures of everything from the beginning so you can have something to refer to WHEN (notice I did not say IF) you have a doubt about which way a part was in place when you took it off. Be sure you get shots of all springs and linkages/brackets related to the carb mounting scheme, those sometimes give as much a head ache as the insides of the carb when going back together.
And of course, also refer to your u toob source.


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RE: gas in the oil of a Kohler engine

Phil - also - being of your age zone, do get that magnifying glass out along with a long piece of stiff small diameter brass wire to probe EVERY orifice in each component of that carb. Some of those holes are darned small and not easy to see, much less to get clean. After probing, blow 'em out with the rattlecan carb cleaner and a shot of compressed air. CLEAN is the name of the game inside that carb. Rebuild using only new gaskets and valve seats.


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RE: gas in the oil of a Kohler engine

Mownie and RCBE, thanks guys---Bifocals really get in the way sometimes, so the magnifying glass is a good idea. On utube, the guy doing the re-build stripped a bit of paper from the end of a twist-tie to gently probe orifices, and it just so happens that I DO have a compressor WITH the necessary trigger-type nozzle ! Your messages were practically carbon copies of the advice I got this morning from a VERY patient man at our local Deere shop, so I've been in good company all ways 'round ! Even HE suggested the use of a digital camera, and I'm glad he did, for over the past 44 years of being with She Who Must Be Obeyed, I STILL have unpleasant memories of linkage problems....(but with mowers, not with her, of course!)


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RE: gas in the oil of a Kohler engine

My VERY mechanically-inclined neighbor, after hearing the particulars of my gas-in oil experience, says that the only way he can think of for that to happen is worn-out piston rings. The mower is 24 years old, and he says that is the probably the cause and the only way for gas to appear in the crankcase...Thoughts, gentlemen? I'd really be much happier if your solutions of a few days ago were correct, and tomorrow when I change air-cleaners and add fresh oil that all will be OK. Today, however, doubt was added...


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RE: gas in the oil of a Kohler engine

Your neighbor is not as mechanically inclined as you suppose he is if piston rings is his first choice for a culprit.
The fact is, gasoline leakage past the carburetor needle valve has been the bane of gravity fed fuel systems since the dawn of the automotive industry.
All it takes is a tiny, irregular shaped piece of crud or fiber, or a flake of rubber from the inside of a fuel hose to get caught in the needle and seat juncture, or for the needle valve to develop a slight indentation that causes it not to seat squarely every time......and gasoline will continue to flow into the carb bowl despite the float pressing tightly against the needle valve.
Though the flow may be very slight, given enough time, it WILL overflow the carb and proceed on into the combustion chamber.
It will then leak down past the piston rings (no matter how new or worn they be) and end up in the crankcase oil.
After the engine is started and warms up with a bunch of gas in the oil, the gasoline will begin to boil and vaporize. This vaporization creates a positive pressure in the crankcase which MUST find a way out. The "way out" will be through the crankcase vent where it flows right into the intake and is fed to the combustion chamber. This flow of gasoline vapors will be full of tiny droplets of oil that have been thrown up because the apparent oil level in the crankcase was raised high enough by the addition of gasoline that the crankshaft is in contact with the oil.
At one time, ALL gravity fed fuel systems had a manual fuel shutoff valve, and if you did not have the sense of mind to remember and shut that valve off, there was a good chance that the next time you went to use the machine........the contents of the gas tank would be found in the crankcase.
Then, the corporate bean counters began calling all the shots at the factory (instead of mechanical engineers) and the manual valves began to disappear.
It was known (amongst the bean counters) that the carb float needle valve would probably serve as a "shutoff valve" until the machine had gone beyond the warranty period, so the bean counters called it a good thing (getting rid of the manual shutoff).
The needle valve was not designed to serve as a fuel shutoff valve to stop the flow of fuel during storage. The needle valve is intended to maintain a fairly constant level of fuel in the carb bowl so that fuel may be drawn out under the influence of carb venturi vacuum (differential atmospheric pressure actually moves the fuel).
Worn piston rings WILL NOT cause gasoline build up in an engine crankcase because at operating temperatures....LIQUID GASOLINE does not exist inside the combustion chamber if that cylinder is firing.
Typically, the leakage of fuel past a needle valve will be so slight that it will not even cause problems with the running of the engine. The rate of gasoline consumption far exceeds the rate of leakage that it adds nothing extra to the air/fuel mixture fed to the engine.
But that slight leak will absolutely drown an engine while it is sitting in storage between uses.
Having a manual shutoff valve and remembering to keep it shut off except when you are running the engine is the only way to assure against drowning the engine with fuel.


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RE: gas in the oil of a Kohler engine

Mownie, I have been chastened by your extremely patient and thorough explanation of the cause of fuel in my Kohler's crankcase. Not only was this SO instructive to me, who will pass it along to my neighbor (sans first sentence, of course), but I hope countless other readers of this web site file it away mentally. I have had a shut-off valve on my 24 year old STX38, and I know I can count one one hand the number of times I've used it (changing fuel filters is all that comes to mind).

As for me, I can say Mea culpa, mea maxima culpa, and thanks a million for your patience !


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RE: gas in the oil of a Kohler engine

Please consider it as less a chastisement, but more of an emphatic illustration of fact and the voice of experience. :^)
As I have often said when I suggest people retrofit their gravity fed fuel systems with a shutoff valve, being able to stanch the flow of fuel from the tank for changing the filter is a PLUS, but not the most valuable reason, saving that engine is numero uno.


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RE: gas in the oil of a Kohler engine

l removed carb, flushed it with cleaner, installed new needle valve , washed air cleaner housing and installed new filters, wicked-out remaining gas/oil mixture from base of oil filter , installed new one, changed oil, turned key and VOILA ! After very brief smoking session to burn off residual fouled mixture of gas/oil, engine is purring like a new one ! All that remains is to install a new fuel filter, and that I will do today. Thanks to ALL of you for your help...


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RE: gas in the oil of a Kohler engine

OK, good report.
Now keep an eye on that oil leak to see if it was just related to the other activity.


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RE: gas in the oil of a Kohler engine

Now, Phil... All we has left to do is to get Mownie to tell HIS age...


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RE: gas in the oil of a Kohler engine

62.33 YOA. But who's counting? :^)


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RE: gas in the oil of a Kohler engine

Mownie's just a young whippersnapper!
I've got 3.33 on him!


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RE: gas in the oil of a Kohler engine

Will do, Mownie. First, I want to spray the mower base and lower engine with Gunk and hose it off so I can really see if there will be additional dripping. Should I run the engine for a while, then drain oil AGAIN and refill it to make sure the oil is no longer compromised, or is what I've done so far sufficient? ...perhaps change oil again at end of season (late November here in Manassas...

Re: age reveals: Good Gawd, Guys! These statements are beginning to sound as if they should be preceeded by "Bless me, Father, for I have sinned..." !


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RE: gas in the oil of a Kohler engine

Phil - you were doing SO good.... LOSE THAT HOSE !!!! Worst thing outside of a power washer you can have around a riding tractor. Use compressed air or leaf blower instead. On the engine exterior, use a petroleum based cleaner and plenty of rags/elbow grease.
You don't want water down in your starter hsg, crankcase, wiring connectors, ad nauseum.... elst you'll be bugging Mownie, Bill and the rest of us here for years to come...


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RE: gas in the oil of a Kohler engine

As far as changing the oil.............if you have already changed the oil and filter, and no additional gasoline has leaked into the engine.........no point in changing it again until just prior to storing at the end of the season of use.
When you get ready to store the machine for winter, I suggest you add gasoline stabilizer to a tank of fresh fuel to "hold" the gas until spring.
I recommend changing the oil as the very last action prior to placing the machine into storage.
After you fill the engine with fresh oil, run the engine for about 5 minutes at max RPM. While the engine is still running, turn off the fuel shut off valve and let the engine run until it uses all the gas in the carb and quits.
These are by no means a complete list of things you can do to protect the machine over winter, but these are related to the problem you just tackled.


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RE: gas in the oil of a Kohler engine

Thanks again, Mownie !


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RE: gas in the oil of a Kohler engine

Well, I am a recently widowed FEMALE who doesn't know anything about small engines but this post almost makes me feel like I can solve my problem myself. My John Deere mower with Kohler engine has been having problems. Looks like the first step is to download the manual. Should I attempt this myself?


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RE: gas in the oil of a Kohler engine

Find a U Tube video of the process. Find an on line source for the specific owner's manual. Judge from those.whether you want to try it.

If the mower has a small leak past the needle valve, it can be managed by using the fuel shut-off.
I would advise you to try .It isn't rocket surgery . I would start with the oil change .


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