kohler command issue

[mowerguy88]

ive got a zero turn with a kohler command ch23s 76586. it ran great all summer. this fall after i mowed for the last time it sat for about 2 weeks and i went to start it so i could service it and get it all ready for next season before i put it away for the winter. well i started it up and it didnt seem to run quite rite so i held my digital tach to both wires and they were both giving me an rpm reading so i know both coils are sending spark. i then misted the muffler right where it comes out of the heads and discovered it wasnt running on the right cylinder. pulled the spark plugs and they were both fouled pretty good so i replaced them and retested. same thing only running on one cylinder. i did a compression test and both cylinders have exactly 190 psi i put a spark checker on the bad cylinder and it has a strong blues spark and it will jump a 6mm gap no problem. i used my inductance spark checker on it and its giving me a high voltage alert on both cylinders which is strange to me. it has vaccum in the crank case while running i havent done a leak down test yet as i have to pull the engine to be able to remove the shroud. does anyone have any thoughts on what it could be before i yank the engine? i dont think its blown head gaskets due to the compression readings. oh ive also removed both valve covers and the valves are operating like they should be on both sides. im thinking its either a bad ignition coil or a compression issue since its so high. i thought these had an auto compression release mechanism if so it must not be working since its got that amount of compression with just the started cranking it. let me know your thoughts please

 

[mowerguy88]

also this unit does NOT have the little black box that electronically controls the advance timing for spark.

 

[EFSM]

The CH23 wasn’t as problematic with the head gaskets as the 25 and 27 hp, but the fouling would concern me. How recently had you changed the plugs?
I don’t believe those engines have ACR. I could be wrong on that though.
Is this a single or twin barrel carburetor? I would guess a single barrel, which means that a carburetor issue is less likely to affect only one side. I have seen an intake manifold gasket blow and create weird issues, but having this issue after sitting for a bit sounds more like an electrical issue.
For a leak down test: could you not hold the PTO end of the crankshaft?

 

[mowerguy88]

It’s a single barrel carb. I thought if Intake leak but it runs too good to be that in my opinion. I would think even with and intake leak it would still fire on that cylinder. Just might not run great. I could remove the pto clutch and try to anchor it there. I don’t think that’s going to yield me any results tho. High comp reading and no tell tale signs of blown head gaskets. I haven’t changed the plugs since last fall. I mow 4-5 acres a week with it. They weren’t that bad really but it was time. I also thought maybe a diode in the kill wire if this model has that but I would think if that were causing issue it wouldn’t spark at all. I’m going to try and get my inspection camera in there tomorrow and see if I can’t disconnect the kill wire on the coil and see if that yields any results. If not I think I’ll pull it and put coils on it. It has to be a spark/ electrical issue. I’ve been racking my brain on this one.

 

[mowerguy88]

so today i pulled the engine, got the shroud off. i did a leak down test and it passed with flying colors. i did an intake leak test and it also passed. i removed the kill wires from both coils no change. i pulled the coils off and swapped them to see if the issue would follow the coil and it did not so the coils are fine. i checked the intake with a scope to verify it wasnt blocked in any way. i then pulled the intake and exhaust off and no obstructions there. the intake valve has a ton of gunk built up on it on both cylinders. and the exhaust has some carbon built up but i wouldnt say any more than normal. i went ahead and pulled the head on the bad side. and as suspected the gasket was not blown and nothing looks out of the ordinary. cylinders are great still have cross hatch and not too much carbon on top of the piston.

 

[EFSM]

Those engines have hydraulic valve lifters. I guess there's nothing wrong there?

 

[mowerguy88]

Those engines have hydraulic valve lifters. I guess there's nothing wrong there?

correct they do have hydraulic lifters, valves are opening and closing like they should they have full range of motion. and they seal according to the leak down test.

 

[Fireslayer]

Look closely at the spark plugs again. Make sure that the one from that side is indeed firing. Make sure there isn't small piece of carbon or debris in the gap and that the gap isn't nearly or completely closed. with a one barrel carb, good compression, good head gasket and leak down tests, you've reversed the coils with no change, about the only other thing is the spark plug. Your only mention about the plugs is that they were changed last fall. May not be, but I'd give I'd give them a good inspection and test on another good known engine and see for sure.

 

[SE#1]

Food for thought: assuming your test results are accurate, another possibility is that it is sparking at the incorrect time.

Have you checked the flywheel key? Possibly sheared key and changed timing a bit.

Since you have verified, spark, fuel, compression, etc......timing could be the culprit.

Another thought: possibly one of the safety features is working, but, shorting while running.

How about a loose or corroded chasis ground? Corroded battery cables?

Spark plug wires chewed on by critter and jumping spark between coil and plug.

Electrical gremlins can sometimes fool you.

Hopefully, this gives you a few more ideas Boss.