1863 no spark and not the interlocks. Please help

[bdudley]

I have an 1863 cub with 837hrs on it with the original deck belt still on it. My father bought it new in 93 I bought it from him. I have been having intermittent spark dropage on a cylinder. It comes and goes. Well yesterday my son took a job mowing the neighbors lawn and he mowed untill dark with the intent to finish it today. We went out to start the old girl up and no spark crank all day long no spark. I've went through the interlocks and disconnected the kill at the engine harness. Still no spark. Yanked engine out of it took shroud off and I believe I found the intermittent spark issue right hand spark plug wire outer coating chewed up. But back to the problem what on the engine would cause both ignition could to not have spark? What does the regulator do? And how do I test the coils/modules there are 2. It has 2 coils 2 plugs and wires and one magnet to trigger. Like I said he mowed 2 hrs yesterday and this morning no spark. I'm ready to pull my hair out please hèlp!!!

 

[jbaker]

Brad, a few post down from yours is one titled 1862 wiring diagram. Try there and see if that helps.

I kinda wonder if your ingition switch is bad

 

[jchamberlin]

Brad, take a magneto and call me in the morning. Seriously, if you've disconnected the kill wire then the interlocks are out of the circuit; if it still won't start, then the most likely cause is the magneto itself.

PDF files available from Wiring Diagrams from the Main Page.

Edit: Forum Sponsor Kirk Engines(above)sells a reasonably priced replacement magneto.

 

[bdudley]

Thought I had it figured out kill wire was rubbed bare behind intake tube. Repaired wire,,,, nope. Still no spark. Where do the coils get voltage from the only wire to them is the kill wire. J chamberlain how do I check the mag. Coming out behind the fly wheel there is two white wires and they run to rectifier. And they are ac current I believe

 

[jchamberlin]

Brad, you are correct about the two white wires, they are the AC leads from the alternator's stator running into the rectifier. The DC coming out of the rectifier charges the battery and runs the lights (if so equipped). If you read the 1862 thread, you will find a citation from the Kohler Service manual which states quite clearly that the energy to fire the plugs comes from the permanent magnet attached to the exterior circumference of the the flywheel. The AC into and DC out of the rectifier have nothing to do with how the plugs are fired; the battery's DC simply supplies the power to the starter necessary to turn the motor over. Once the motor is turning over, the magnet supplies the energy to fire the plug.

As it passes the primary coil, the magnet's field induces a current to flow in the primary coil's windings. The 200 volts or so in the primary gets stepped to 20,000 volts in the secondary which is enough to fire the plug. HOWEVER, in order to induce the current to flow in the secondary coil, the current through the primary coil's windings must be interrupted or "broken" in order to "trigger" primary field's collapse. The field collapse can be triggered by either breaker points or electronic ignition. I'm not sure, but I suspect your 1863 employs an electronic circuit to "trigger" the coil, and I think the electronic circuitry is the most likely point of failure in your case. I don't know of any other way to diagnose it other than to replace the magneto itself, set the air gap, and hope it works. Again, there isn't 12 volts leading to it to check out, and there is no easy or practical way to separate the triggering circuit from the coil windings: everything is internal to the magneto's "package."

By-the-way, you say you have two coils, by which I interpret you to mean two secondary coils (since there are two spark plug wires), and you may, but I know for certain that you only have one spark. That is, the M18 in your engine employs a "wasted spark" system. Both spark plugs fire at each revolution of the crankshaft. One plug fires on the compression stroke of the first cylinder; while the other plug fires on the exhaust stroke of the second cylinder, or is "wasted."

I was rather surprised to learn that the coil packs on my 4 cylinder 1997 GMC Sonoma (same as Chevy S10) employed the same wasted spark system.

I understand that the magneto is a common point of failure on M18s, if that helps. Good luck.

 

[bdudley]

The only wire to the coils(kohler calls em ignition modules) is the white wire to ground only(kill). Does current pass through the magnet on the flywheel or is it just the trigger? I'm sorry for my stupidity but I'm not understanding how the magneto feeds the coils. I know my system is 20amp cd ignition. Model number of my engine is ch18s.

 

[bdudley]

I got on cub cadet link to look up parts and all that was listed was a stator?? No mag. On Atvs the stator is usally for power generation for lights etc. the diagram shows a mag I guess I'm gonna pull engine again and yank fly wheel off and see what's back there. I had it apart yrs ago to replace rear main seal but been to long to remember Keep info and ideas coming. I will get her fixed. The no spark demon won't beat me yet

 

[bdudley]

Ok finally got time to read thru the 1862 posting below. That explain most of my previous post. Ok so the magnet on the flywheel rotates past the coil energizes it goes through the step up process and is discharged thru the plug as a spark. So to stop this of course you ground the coils no spark. Interlocks ground the coils no spark. I unhook the kill from the engine harness which deletes all interlocks and key switch kill aswell so why don't I have spark? No way both coils (ignition modules)went bad at the same time. The stator puts out ac to rectifier leaves rectifier and goes back to the wiring system as dc current. Is that why the stator is bad? Not producing dc current back to the system? Can I test that at the rectifier? Could the rectifier be possibly bad? I am a single income family of four and money's tight don't have hundreds of $ to throw parts at it. Hopefully now you know why all the question.... Looked like stator was 85 bucks rectifier was 45 ign modules like 65 bucks apiece thanks for the help keep it coming

 

[bdudley]

Oh yes I also checked air gap and set it at .011 in with feeler gauge under all three legs as the Koehler site recomends. Could magnet be weak on the fly wheel should I close up air gap more?

 

[jchamberlin]

Brad, I think you're going to have to change out the magneto.

The charging system is totally isolated from the ignition system.

Don't worry about the stator or rectifier right now, you have to get the engine running before you can check them out anyway.
As long as you can crank the engine over you can continue to solve your ignition problem.

Replace the magneto as cheaply as possible and see if it doesn't start up and run, but be sure to have a way to kill the magneto before trying to start the engine.

Have you tried posting in the Classified's "Want to Buy" section? You might be pleasantly surprised at the results.

Edit 1: When you have the flywheel off you can check the stator for continuity and for a short to ground.

Once the motor is running you can check for AC into the rectifier (pull the connector back to insert test leads, but leave the wires connected) and DC coming out of the rectifier. To check for AC put a test lead on each wire coming from the stator. (Do not go to ground or the chassis.) To check for DC go from ground to the wire "going back into the harness" as you put it. You should be seeing something like 30-40 volts AC going in and 13+ volts coming out.

Edit 2: Results of test with flywheel off: If the stator is open, it is bad; it may be connected to ground for a reference, but I wouldn't think so. I would use the reading to ground for information only and reassemble the motor for a running test before deciding whether the stator is bad. Of course, if you don't have continuity between the leads it will need to be replaced before you reassemble the motor. But again, the stator has nothing to do with producing the spark in your CH18.

Edit 3: I don't think the magnet's fields weaken over time, that's why they call it a "permanent" magnet, and it is pretty strong if I recall. Try pulling a screw driver away from it.

 

[bdudley]

Ok thanks a lot. Where is the magneto located?

 

[bdudley]

Took engine back out closed air gap to .008 in cranked it on bench still no spark so I guess I'm going to be replacing both ign modules. Totally unhooked ground from them to eliminate them to eliminate that. Still no spark so that's all it can be. The wiring diagram shows yellow to white and to the " mag" which is actually the ign modules. Just find it hard to beleive that they both went bad at the same time at the top of the coil by the horse shoe the epoxy is cracked on both of them which on cars let's moisture in and eventually takes em out so I suppose it's possible. If any one needs help pulling the engine on a cyclops style I got it down to a half hr lol

 

[bdudley]

Ok guys problem solved. Bought two new ignition modules and installed the and it fire right up. Thanks for all the helpful advice!!! It still blows my mind that they both went at the same time. It musta been one weak and when it spun fast enough made the other fire. When the good one got weak neither would fire. Put them on and cranked it on the bench. Had everything hotwired. Lol got tired of putting it in and taking it out

 

[bdudley]

Just mowed three hrs no intermittent spark starts great, runs better than it has for yrs

 

[jchamberlin]

Glad you got it running, Brad. Don't feel too badly about having to pull the motor so many times, many of us have gone through the same rite of initiation.
You do learn to check everything out well before closing it up (as in thinking to yourself, "I had better clean and lube that starter while I'm here").