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I picked up a JD LX255 for parts but noticed the engine had compression so I figured I'd take a shot at it. Almost all of me engine repair work has been with horizontal shaft engines, and mostly older ones at that so my experience with larger vertical shaft engines is quite limited. I have no experience with Kohler engines. This JD has a 15 hp Kohler, Model CV15S, Spec # 41571, Family: SKH426U1G2RB.

The engine would start using starter fluid and would stay running (barely, and rough at that) with continuous spray of starter fluid but it smoked terribly and would eventually die. I figured I had a carb fuel delivery issue and a blown head gasket. So I finally got the OHV and head removed, much more difficult than an old horizontal Briggs! When I removed the head I noticed a mix of gas and oil running a steady stream out of the valve rod openings. Since my experience with these engines is limited I didn't know if that much oil should be coming out of there but the fuel in the oil was very concerning. I didn't see any significant defects in the head gasket. The cylinder head was good, valves looked good, cylinder bore was spotless. I drained the oil and it was obvious there was a lot of gas mixed in the oil.

Without tearing this engine down any further at this point, can someone tell me what I am likely dealing with? I wondering if it's worth going any further.

What is the chance the tank was filled with an oil-gas mix by mistake?

I doubt that happened but how would that explain fuel in the crankcase?

For small engines, gas in the oil is usually one of two things.

Most common, a stuck needle valve in the carb allowing gas to pour unchecked into the combustion chamber, where it seeps past the piston and into the crankcase. Usually when the engine is not running. Many recommend a fuel line shutoff be put in line to stop this if you can't easily or quickly correct this problem in the carb.

Much less common, severely worn piston rings allowing some fuel to enter the crankcase.

There may be other issues with that engine I am not aware of, but these are the common causes of gas in crankcase oil that I have been exposed to. Whatever the case, it is obviously not a good thing to have gas in your crankcase oil. You need to address this, as you are doing, and remedy the situation quickly. Don't allow the engine to run with gas in the crankcase.


Good luck.

If the carburetor has a brass float check it for gasoline inside the float. They don't float too well in that condition and it leaves the needle valve open for gas to run where ever it likes and sometimes into the crank case.

Good info, I've dealt with those leaking floats before but with a horizontal engine it doesn't cause these issues. I'll rebuild the carb and put on a new head gasket and see what happens. I'm trying to avoid opening the crankcase.

On a good note, at least the crankcase is clean, that old oil had so much gas in it that it ran out like water.

I just called up the blowup of your engine, and it has a mechanical fuel pump which could easily be your culprit!!!

Fish said:

I just called up the blowup of your engine, and it has a mechanical fuel pump which could easily be your culprit!!!

Click to expand...

DING DING DING! Nice Catch! Yes, OP, absolutely. Had no ideal there was a fuel pump involved.

This makes sense, the people told me that they had the fuel filter replaced but that didn't fix it so they parked it. It may have fixed the problem but if they never dumped the bad oil it wouldn't a time right. That makes sense. Might not be a carb issue at all. I'll still give the carb a good makeover since I have it off and we'll see what happens. Thanks folks!

Man, I don't even know what I thought I read.


:ashamed:

Which post?

Fuel pump, sorry, they said they had the fuel pump replaced, not fuel filter. I cleaned the carb, plastic float not metal. There is a small actuator type device on the bottom of the carb bowl, if it was stuck in the open or out position it would not allow any gas into the center chamber of the carb, if it was stuck in the "in" or back position then gas would overflow into the carb. There is a wire from that little actuator to the ignition panel. I don't know how to test to see if it is working correctly. I removed the fuel pump, and in spite of what those people were told, it had not been replaced. The diaphragm had some good cracks in it.

Could any of this be the culprit? I'm still having a hard time understanding how the fuel would get into the crankcase.

Oh brother, don't tell me I can't just buy the replacement diaphragm. All I'm seeing is the "fuel pump kit" which is basically just a replacement fuel pump, and not cheap at that.

Fish said:

I just called up the blowup of your engine, and it has a mechanical fuel pump which could easily be your culprit!!!

Click to expand...

I had that problem on my Kohler command. The diaphragm in the fuel pump had worn thin and gas would pass right through it into the crankcase. I changed fuel pumps and the problem was fixed.

That sounds like the problem then. So is there anywhere to get just the diaphragm? I've broken down the fuel pump and its a pretty simple swap I just can't find one. I hate to replace the entire fuel pump.

bt3 said:

For small engines, gas in the oil is usually one of two things.

Most common, a stuck needle valve in the carb allowing gas to pour unchecked into the combustion chamber, where it seeps past the piston and into the crankcase. Usually when the engine is not running. Many recommend a fuel line shutoff be put in line to stop this if you can't easily or quickly correct this problem in the carb.

Much less common, severely worn piston rings allowing some fuel to enter the crankcase.

There may be other issues with that engine I am not aware of, but these are the common causes of gas in crankcase oil that I have been exposed to. Whatever the case, it is obviously not a good thing to have gas in your crankcase oil. You need to address this, as you are doing, and remedy the situation quickly. Don't allow the engine to run with gas in the crankcase.


Good luck.

Click to expand...

Typically, that's usually the problem. (The stuck needle valve in the carb)

I had a Neiko carb on my engine, and although the needle LOOKS good, it was plastic-tipped, and when the plastic hardens with age, it will not seat tightly enough to keep the fuel from over-flowing the bowl, and I've had the crankcase fill to the extent that it filled all the way to the bottom of the intake manifold.

Good answer.

arch252 said:

That sounds like the problem then. So is there anywhere to get just the diaphragm? I've broken down the fuel pump and its a pretty simple swap I just can't find one. I hate to replace the entire fuel pump.

Click to expand...

I thought the same thing. The diaphragm was easily removed, but I couldn't find a replacement so a new pump was my only choice.