1864 - Kohler CH18 Power Loss

[kruss77]

I have a model 1864 Cub Cadet with a Kohler CH18 engine that I知 having power loss issues with. Here are the details:

- Bought used in 2002. Ran great with NO problems until about 6 weeks ago.
- Power loss coincided with the replacement of the carburetor solenoid (perhaps just coincidental). (Previous owner had ground down the pintle on the old fuel shutoff solenoid. This is used to stop the flow of fuel to the carburetor jet to prevent backfiring when shutting down the engine.
- New solenoid appears to operate fine. Can see it working when looking down into the open carburetor fuel bowl.
- Power loss coincided with the removal and reinstallation of the fuel tank (perhaps just coincidental). (Same time as carburetor solenoid replacement.)
- Rebuilt the carburetor - no improvement.
- Rebult the fuel pump - no improvement.
- Replaced the fuel filter (3 times) - no improvement
- Thinking maybe there was water in the fuel, I flushed out the entire fuel system; replaced old fuel with fresh fuel no improvement. Replaced old fuel lines with new at the same time no improvement.
- Sometimes the power loss occurs immediately upon starting. Sometimes not until after a couple of laps around the yard.
- It will start and idle OK, but as soon as the engine sees a load, it loses power making it almost impossible to mow (or anything else for that matter).
- Engine still runs, just at a reduced power output and does not backfire or misfire.
- Sometimes the power goes in and out like someone is flipping a switch. Loss of power behavior is very erratic.

Is it possible the coil is going bad? Would that produce these kinds of symptoms?

 

[OldMachinist]

It's possible the governor linkage or spring was reassembled wrong or the governor linkage is just sticking.

 

[kruss77]

The governor has never been disconnected and operates the same way it's always operated since the day I got it. This failure SEEMS to be fuel related, but I know the fuel is now good. Of the three things needed to make power (air, fuel, spark), I know it's getting plenty of air and flenty of good fuel, so that's why I'm suspecting the coil.

Does anyone know if a failing coil (ignition module) can create these symptoms as it's going?

 

[rcbe]

If not done already, might try a new set of plugs - one of 'em may be breaking down and not be firing under load.
Also, for addt'l help here's a link to a service manual for that engine:

http://www.kohlerengines.com/onlinecatalog/pdf/tp_2428_b.pdf

 

[kruss77]

Brand new plugs (changed at the same time as the new carburetor solenoid).

Thanks for the link to the Kohler service manual, but I've been all through it and it doesn't help with the symptoms I have.

I'm hoping that someone can tell me what happens to a coil when it's dying.

 

[Dave01]

I agree with you that its most likely an ignition problem. Have you removed both spark plugs, grounded them, and cranked the engine to look for spark? The power loss you describe could be one cylinder cutting in and out, they run surprisingly smoothly on 1 cylinder, just lack power.

You certainly can have an ignition problem that comes and goes, might get worse with heat. The "power coming in and out like flipping a switch" is the key. A few other things I'd try - when you lose power, pull one plug wire at a time and see if one makes it die, the other makes no change, to isolate which cylinder is firing. Then, run for a minute that way (during the power loss cycle) and shut down, quickly pull the plugs and see if one is wet, one dry. That way, if you isolate the problem cylinder, and also see that the plug is wet, you'll know its ignition and not fuel related.

I hope this helps, and good luck.

 

[kruss77]

I agree with you that its most likely an ignition problem...

BINGO! It was an ignition problem. As I'd mentioned previously, I'd gone through just about everything else that produces similar symptoms with no luck. Figuring I only had one thing left to replace, I pulled the motor this weekend, replaced both coils, and viola: problem resolved! (I also found a bare wire leading to the coil who's insulation had obviously been chewed off by a critter -see photo. I repaired that as well.)

Thanks to all for their advice!

 

[kruss77]

The power loss you describe could be one cylinder cutting in and out, they run surprisingly smoothly on 1 cylinder, just lack power.

That's the weirdest thing about it: the motor ran smoothly (no backfiring, no coughing or sputtering), it just lost power.

You certainly can have an ignition problem that comes and goes, might get worse with heat.

It did get worse with heat: I mowed one day when the temp was around 65* outside and it ran fine the whole time. The next week it was around 78* when I mowed and as soon as the motor reached operating temperature it lost power.