# kohler 16.5S wont start



## jetmech_25 (Oct 30, 2010)

Hello. I have a Sears Craftsman mower with a kohler 16.5S engine that i was using to cut fairly tall grass (heavy load). As I was mowing, it randomly backfired twice, kept going, then backfired again and died. Did some troubleshooting, compression is good, but with a weak spark. replaced ignition module and rectifier. Great spark now, but same issue. Engine cranks fine and after a couple of failed start attempts, it backfires out the exhaust, so I'm thinking its a timing issue. Removed the flywheel hold-down bolt and notcied a v-shaped paint mark on the shaft. Is this a factory slot mark? If it is, the flywheel key is roughly 220 degrees away from that mark and is maybe a 1/4" down inside the slot on the flywheel. I have no puller and no way to remove the key. Just wondering if I'm headed down the right path before I try removing this flywheel. Thanks for your input.


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## 30yearTech (Sep 14, 2006)

The flywheel key is a woodruff key and you can't tell whether it's broken or not without pulling the flywheel. Chances are the key is your problem. Pull the flywheel and have a look at the key.


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## jetmech_25 (Oct 30, 2010)

Pulled the flywheel, key is fine. Reinstalled and tried it again just to verify i was back to square one. If i put it on choke, it cranks 5 or 6 times and lights off enough to disengage starter, but wont run at all. Second attempt causes a backfire out the exhaust. even tried starting fluid once, but got an immediate backfire. As far as I can tell, the only thing left as far as ignition is the Speed Advance Module. Any way to bypass this?


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## jetmech_25 (Oct 30, 2010)

btw, i already removed and cleaned out the carb and obviously changed the spark plug.


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## scrench (Dec 8, 2004)

Did you check the compression.does it whiril over really fast? Sounds to be in the ex side valve. (Ie) stuck open. (Not closing all the way) I wouldn't jump to the sam just yet. Could have a blown head gasket. You need to check the compression. Or just pop the valve cover and head and check it out. Could have a bent or broken pushrod. Valve spring might have came off. I would pull the head.


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## jetmech_25 (Oct 30, 2010)

compression check got 40psi on first rev, up to 80psi by 3rd or 4th rev...3 consecutive times. Doesnt seem to be a mechanical problem.


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## jetmech_25 (Oct 30, 2010)

Also verified again that i have a float bowl full of fuel and the solenoid at the bottom of the carb has 12v going to it with the key on, 9v while cranking.


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## scrench (Dec 8, 2004)

Un plug the kill wire on the coil. The one that should be on the bottom. And try it.


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## jetmech_25 (Oct 30, 2010)

removed the solenoid from the bottom of the carb and verified it retracts with power applied. If I'm not mistaken, this should verifiy that all of the safety stuff is working.


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## scrench (Dec 8, 2004)

No. Has nothing to do with the safety switches that's a anti back fire solenoid. When you pull the wire off the module that will eleminate all the safety switches. You have to be prepared to kill it if it does start.you have to short it to kill it. I have a spade with a short wire I put on before hand.


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## jetmech_25 (Oct 30, 2010)

No idea where that is. If you mean on the ignition module, only 2 wires on it, both go to the SAM


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## scrench (Dec 8, 2004)

What's the model number on the motor


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## jetmech_25 (Oct 30, 2010)

oh, and a ground to the housing. the other 2 wires are brown or yellow.


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## jetmech_25 (Oct 30, 2010)

kohler model cv16.5S-43527


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## scrench (Dec 8, 2004)

Nake sure the ground is grounded good


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## jetmech_25 (Oct 30, 2010)

grounded by bolt that holds ignition module to crankcase, wire goes into SAM.


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## jetmech_25 (Oct 30, 2010)

sorry, model # is actually a CV16S


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## jetmech_25 (Oct 30, 2010)

disconnected white "kill" lead near SAM and placed a toggle switch in line as a manual kill. no difference with switch on or off.


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## jetmech_25 (Oct 30, 2010)

Still lost. no ideas?


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## 30yearTech (Sep 14, 2006)

Have you checked to see if your getting power to the sam when the key is in the on position? Could be your loosing power when the key is released from the start position.

You can download a service manual for your engine at www.kohlerplus.com just enter as a guest and the manual will have a testing procedure for this type of ignition.

Best of Luck... :thumbsup:


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## jetmech_25 (Oct 30, 2010)

I do have the manual and it states that I must have a special ignition tester to get accurate readings with the smart spark system. Just using a voltmeter "will give erratic readings". Spark seems excellent with the plug removed and it seems to be firing inside the engine as it does attemp to start and backfires. Can't see any water in the fresh gas, but I'll get some gas from a different place today and try that. Noticed that there are splices in the A and C wires going to the rectifier. The splices read good, but aren't shielded. Maybe this is causing a problem? Can't imagine that it would be a carberator problem as no adjustments have been made. It will atempt to start on full choke, then backfire on second attempt. If, after the first failed attempt on full choke, I move the throttle to lowest RPM, it tries to start again, but can't sustain ignition. I have yet to remove the valve cover, as compession is good. Will get some different gas and look for power at the SAM today and let you know.


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## 30yearTech (Sep 14, 2006)

All I have ever used is a multimeter to test for voltage *to* the sam. You want to make sure you have power when the key switch is released from start. If you are not getting power in the run position, you will loose spark and if your carburetor is equipped with an after fire solenoid it will also stop fuel to the main jet. The wiring to the voltage regulator/rectifier should not be a cause of your issue, of course if the splices are not good, then your battery may not get recharged.


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## jetmech_25 (Oct 30, 2010)

Put some 92 octane gas in it today and it will almost start, chugs a couple of times, but that's it. I have 12v at the red wire terminals as it enters the SAM with ignition switch in start or run. Exiting the SAM and attaching to the coil, brown has 2.5v while cranking, yellow has nothing.


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## jetmech_25 (Oct 30, 2010)

Any good links on the tools to do a compression leakdown test?


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## 30yearTech (Sep 14, 2006)

Here is a link to one from Harbor Freight. It's an inexpensive one, but will work fine to troubleshoot your engine.

http://www.harborfreight.com/catalogsearch/result?category=&q=leak+down+tester


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## jetmech_25 (Oct 30, 2010)

Thanks! I am having a very hard time finding the correct output chaft size for this engine. Any ideas on where to find this info? Considering just repowering it. Already spent more than half the price of a new turn-key engine, and considering its age, probably worth doing. Looking at a Kohler 18hp Courage with a 1" X 3 5/32" straight (not tapered) output shaft, but no idea what the CV16.5S-43527 engine has.


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## usmcgrunt (Sep 16, 2007)

jetmech_25 said:


> Thanks! I am having a very hard time finding the correct output chaft size for this engine. Any ideas on where to find this info? Considering just repowering it. Already spent more than half the price of a new turn-key engine, and considering its age, probably worth doing. Looking at a Kohler 18hp Courage with a 1" X 3 5/32" straight (not tapered) output shaft, but no idea what the CV16.5S-43527 engine has.


Try this link for info on the different Kohler replacement engines and dimensions.Hope it helps.

http://www.smallenginesuppliers.com/shop/html/pages/kohler_vertical_engines.html


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## jetmech_25 (Oct 30, 2010)

That link offers 1 Murray engine with the same shaft size as the kohler 18hp I want to use, so I'm thinking it'll work. Thanks!


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## 30yearTech (Sep 14, 2006)

1" X 3-5/32" is the most common size shaft, but that does not mean that is what your engine has. You can remove the drive pulley and measure the shaft.


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