Kohler running on one cylinder

[jdgreg]

I've searched and read several threads here of similar issue as mine, and it sounds like my problem might be an ignition coil. I have a Simplicity Legacy mower with a Kohler 25. I was mowing on a slope when it started running very weak. I looked at the fuel gauge, and though I had about 1/2 tank, the slope was to the right, so the gauge was on E. I figured the fuel pickup was not getting ample fuel supply.

So I disengaged the mower, and eased it onto level ground, and worked the choke a little, which had no effect on it. Made it back to the garage, barely. I cleaned off the foam pre-screen, checked the plugs, checked the harness connector on the right side, all looked ok.

I narrowed it down to running on one cylinder, as I could pull the right spark plug wire off, and it had no effect. When I pulled the left, it would stop running. I swapped plugs to make sure it wasnt a bad plug, but the problem did not follow the sparkplug.

I connected an old Sears timing strobe light to each plug wire as it was running, and both sides made the timing light come on the same brightness.

I dont think it is fuel related. I filled up the tank, and ran it (on one cyl) for a few moments, no change. If the carb had clogged passages, choking it would have a more positive effect on how it runs, and both cylinders would be running, even somewhat intermittently. Now, only the left cyl is running.

Suggestions?

 

[jdgreg]

Just came in from checking the compression, left is about 160 and right is about 170. So the problem is most likely electrical?

Oh yeah, and my son had been mowing for about 2-3 hrs prior to when I got on, so everything was heat soaked pretty good when it started acting up.

 

[greasemonkeyok]

Bad spark plug wire? If I understand your posts, the cylinder with the higher compression is not firing.

 

[jdgreg]

Bad spark plug wire? If I understand your posts, the cylinder with the higher compression is not firing.

Yes, right cyl - 170# compression, is not firing. Plug is sparking though. I guess could be plug wire, Smart Spark module, or ignition module? Maybe air gap wrong? Mice are always making a nest around the drive shaft, maybe they chewed on some of the wires ????? I really dont want to pull that engine. :confused2:

 

[2manyrocks]

I'm a little confused. One cylinder isn't firing, but that cylinder has spark?

I just got through replacing a $35 ignition module on a single cylinder Kohler magnum--all I had to do was pull the sheet metal shrouds off and replaced it with no problem. That cured mine going dead after it got hot. I didn't have to pull the engine--just took my time and it went fine.

 

[Jim Thompson]

I would remove both rocker arm covers and both spark plugs. Then rotate the engine by hand while observing the behavior, lift and condition of the rocker arms and push rods. Kohler had problems with the rocker arms on the earlier Command engs and have upgrade/ replacements available.

 

[jdgreg]

I'm a little confused. One cylinder isn't firing, but that cylinder has spark?

I just got through replacing a $35 ignition module on a single cylinder Kohler magnum--all I had to do was pull the sheet metal shrouds off and replaced it with no problem. That cured mine going dead after it got hot. I didn't have to pull the engine--just took my time and it went fine.

Yes, the right cyl is not firing, but has spark. I've verified with the sparkplug grounded against the head while cranking it, and with a strobe timing light. I've swapped plugs and the problem stayed with the cyl, so it's not plugs. Since it has spark, it could be a timing issue.

 

[jdgreg]

I would remove both rocker arm covers and both spark plugs. Then rotate the engine by hand while observing the behavior, lift and condition of the rocker arms and push rods. Kohler had problems with the rocker arms on the earlier Command engs and have upgrade/ replacements available.

If there is a problem with the rocker arms/valves, wouldnt it show up in the compression? The right cyl (no run) is about 170 and the left (that runs) is about 160.

Thanks for the suggestions. Still scratching my head. I plan on stopping by the shop today and see if they can test the components if I bring them in.

 

[Jim Thompson]

Not necessarily, I've seen some strange indications resulting from bent push rods and broken rockers. I suggested this because it is a quick and simple test and frequently renders conclusive results.

 

[jdgreg]

Not necessarily, I've seen some strange indications resulting from bent push rods and broken rockers. I suggested this because it is a quick and simple test and frequently renders conclusive results.

Good point. I just pulled the rocker cover off, and cranked it over (plugs out), and everything looked good.

Now I have a bolt to replace and a hole to retap. Seems the factory cross-threaded it. I knew it would snap off, but didnt. Seems like always something .....

 

[jdgreg]

The shop pretty much agreed it was electrical. I ordered the spark module, will be in tuesday. Hopefully that is it.

 

[Jim Thompson]

Sorry i led you astray and that checking the rockers and push rods resulted in the broken bolt. I've done that a few times myself. Hopefully the ign control module will fix it. Did the repair shop test it or are they just assuming that it's the likely culprit?

 

[Sackett2]

will be watching for a conclusion, for I would be leaning at a fuel issue- the reason being, spark is present, compression is good, and that one cylinder is running says mostly, timing is ok.
Let us know...

 

[jdgreg]

I would suspect carburetor, certainly easier than dealing with the coils. However, the right plug is wet when I pull it, so in my mind that rules out carburetor. The module will be in tuesday. I just pulled the engine so I could get to module wiring. I have half a mind to go ahead and order the right coil as well. I really dont want to pull it a second time. :confused2:

 

[jdgreg]

Sorry i led you astray and that checking the rockers and push rods resulted in the broken bolt. I've done that a few times myself. Hopefully the ign control module will fix it. Did the repair shop test it or are they just assuming that it's the likely culprit?

No problems, better safe than sorry. A tap and new bolt and it'll be as good as new. What really torqued me off was all 4 of the 8mm head bolts (two on each side) that bolt down the top of the back plastic housing (one side the bolts also secure what looks to be like an engine hoist bracket), they all snapped right off!!!! A little anti-seize at the factory would have been nice.......

I asked the shop about testing the module, and they didnt seem like it was something they normally did. Which seemed a little odd, cause I know they can be tested. After I gave them the run down, and what I had done, they pretty much agreed, it sounded like either the module or the coil. Well see this week.

 

[_RaT_]

If you have separate carbs for each cylinder then I could see it possibly being the carb, a quick and fast check is a quick shot of WD 40 in the intake with the engine running in the non producing cylinders carb, if it picks up for the moment, its fuel related, if not, its most likely electrical, coil, plug, timing.

 

[zzvyb6]

Run it on one cylinder until it gets warm. Then swap spark plugs and see if the other cylinder gets hot. You could have a bad plug. Yes, it sparks outside in the open, but under compression and a fuel charge, it may not. This situation is very common with the use of e85 (15% ethanol) gas. This fuel also deteriorates carburetor rubber parts and fuel lines unless the motor is equipped to handle this fuel.

 

[jdgreg]

Only one carb, I tried putting a little Sea Foam in while it was running on one cyl (left one), and it made no difference. Nor did adding a little choke.

It was hot when I did the initial troubleshooting. I swapped the plugs, and the problem stayed with the cylinder. So I think the plugs are good. :confused2:

 

[BTI]

Almost always is a bad coil.
Replace both.
Both will fire, but one will fire intermittently or not at all.
Just depends on how bad it is.

BTI

 

[jdgreg]

Almost always is a bad coil.
Replace both.
Both will fire, but one will fire intermittently or not at all.
Just depends on how bad it is.

BTI

Noted. I called and ordered the coil as well. Hopefully it should all be in by the next day or so. If it's not, I gonna have to find someone to hay my yard. :laughing: