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HotRod53

Kohler twin won't shut off 1 cylinder

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HotRod53
First off, my Simplicity model number is missing...sorry. The engine is a Kohler C8203, spec #64512, ser #2227912037, 20 hp with a Sunstrand hydro 20. This model also has PTO, power steering, and hydraulic deck lift. Update: we think it's a 1691339 Sunstar hydro 20 This started a while ago, turn off the key and one cylinder shut down slowly and one went off immediately. I traced the wiring from the ignition switch to the white wire going into the coils. We took the covers off and checked the white wiring to the coils where it splits. We replaced all wires and cleaned everything....still the same problem. Any suggestions?

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UCD
1691339 is the MFG# for the 60" mower deck which is original equipment for a Sunstar 1987-89 MFG# 1691381 SunStar-20HP (20GTH) 1988-90 MFG# 1691381 SunStar-20HP (20GTH) MFG# 1691710 SunStar-20HP (w/Lift & P.T.O.) 1990-92 MFG# 1691926 20 GTH (SunStar) 1992-94 MFG# 1692133 SunStar-20HP 1995-97 MFG# 1692454 SunStar-20HP MFG# 1692456 SunStar-20HP MFG# 1692135 SunStar-20HP

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Al
HI, Need to check on this. But I believe the kill wire {white) that goes to the coils has a diode in the lead to each coil. This prevents the coils from interacting with each other. Without the diode isolation the transients on the kill wires would feed into the opposite coils and neither would function. I know the Briggs Vangards have diodes in the kill line, and now as I think about it I believe Kohler puts them in the coils themselves. Anyway one of the coils has an open diode in the line to kill the engine. The diode may be in the coil or the wire. One of the coils is getting grounded to kill it and the other isn't. Then the fuel anti-afterfire solenoid is killing the engine. The 180 degree opposed twins used a system that supplied spark to both cylinders at the same time. This was called a wasted spark system. Since mechanically the engines were at top dead center at the same time, one at fire the other between intake and compression the easiest solution was to use a coil with 2 secondaries and fire both plugs simultaneously. The V twins cannot use this system because they have a long space between one cylinder and the other and the next has a short space. Hence the need for separate coils. Al Eden

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MikeES
By serial number your engine was built in 1992. If it is original your tactor is either a 1992 or maybe a 1993. If you have an opposed twin your engine should be a model M20S (Magnum 20hp electric start). Spec number should be "495xx" with xx an engine variation code. With a model number C8203 and Spec number "645xx" this sounds like a Kohler "Command" V-twin. Are you sure that your engine model is not CH20S? Which is the Command 20hp V-Twin. Sorry, I did not see the other post on this subject. Someone else had already figured that this was a command engine.

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HotRod53
Based on Al's description, we tore into the coils again. We found that we had resistance from the kill terminal to the plug wire on the coil that will shut down, and no resistance on the kill terminal on the cylinder that will not shut down! The resistance is polarity sensative just as it would be if measuring across a diode. Al, you just may be my hero! We're going to the dealer tomorrow to buy a new coil module and we'll see whay happens. I'll let you know.

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HotRod53
Al.....you are the man! We replaced one module and the problem is fixed! When I measured the resistance between the plug wire and the kill terminal of the new module, it was the same as the one that we suspected to be good. We installed the new module and all is well. This was my first time using this website, between the access to the manuals and the obviously qualified help, it made the job a lot easier. Thanks to all!! (and AL)

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