coil questions

Andy C

Member
I am working on a Kohler Magnum 20 2 cylinder engine. There is not a spark. I have taken the coil off and cleaned the coil steel part and the magnet on the flywheel and then put the coil back on with the specified .010 inch gap. Still no spark. I have applied 12 volt + to the tab (see picture) Does anyone know how to check coil with an ohmmeter and what the values should be ? Any other suggestions for checking/troubleshooting ?
Thanks in advance!
cvphoto150743.jpg
 
Any other suggestions for checking/troubleshooting ?

Substitution is the best test.

I have a 20 hp kohler command. I bought a new coil.

Then I put a want ad on craigslist for a blown kohler engine.
I removed all parts, carb, charging coil, voltage regulator, ign coil, starter. Then I sold the engine block for parts and got all my money back.

I now have a box full of free spare parts for testing.

I use 3 dollar bills between the magnets and the coil. The dollar bills are close to 0.10 inches.
 
That is the grounding tab for shut off. After 12V put to it, if it wasn't bad before, it is now. Kohler manuals are available free on their website. Buy only an OE coil, expensive, but worth it for lack of hassle.
 
(quoted from post at 09:39:56 03/24/23) That is the grounding tab for shut off. After 12V put to it, if it wasn't bad before, it is now. Kohler manuals are available free on their website. Buy only an OE coil, expensive, but worth it for lack of hassle.
ight
 
There's a good guy on U tube called Taryl fixes all. He has a good video on this. Done with a little humor.
 
Rust on the flywheel magnets and rust on the surface of the coil has no effect on spark. Sanding off the rust doesn't make any difference. It's just an old wives' tale told by people who think they know how small engines work.

That is a plain old magneto coil. No battery power is necessary. The terminal is for a kill wire, and putting 12V to it probably didn't do the coil any good. Not that it was any good to begin with.

Long story short you've got a bad coil. No spark with the kill wire removed is troubleshooting enough. No need to measure ohms.
 
AS far as any ohm meter checks, they can ONLY tell you if a coil winding is BAD like totally open HOWEVER even if it has good continuity it can still be BAD as it typically breaks down under HIGH VOLTAGE actual operating conditions....Make sure theres no kill wire circuit to ground. I always cleaned up the flywheel magnets and set the correct gap. If still no spark with NO kill wire shorts, its sooooooo often a BAD COIL.

John T
 
(quoted from post at 12:19:10 03/24/23) AS far as any ohm meter checks, they can ONLY tell you if a coil winding is BAD like totally open HOWEVER even if it has good continuity it can still be BAD as it typically breaks down under HIGH VOLTAGE actual operating conditions....Make sure theres no kill wire circuit to ground. I always cleaned up the flywheel magnets and set the correct gap. If still no spark with NO kill wire shorts, its sooooooo often a BAD COIL.

John T

That isn't imply a ''coil'', it's in effect a self-contained electronic ignition unit, with transistor(s) and other electronic components encapsulated along with the coil windings.

If it doesn't ''fire'' when assembled to the engine with the ''kill'' wire unplugged from it it's ''dead''.

NOT to mention the fact external voltage was applied to it!
 
Want to say thank you for all the replies! When I read that the wire is the kill switch I felt pretty dumb and realized I had made some assumptions. We all know what that means!
Have a coil coming this week and will go at it again.
 
Thanks for your feedback Have a coil coming this week and will go at it again.

Sounds like a good plan, as most of us basically agreed, if there's no fire and no kill switch ground LIKLEY A BAD COIL ALSO if you applied 12 volts it may have fried the coil grrrrrrrrrrr

John T
 
To really test, an inductance testing piece of test equipment for an actual number....but you don't know what the design spec of your particular coil happens to be, or an oscilloscope and a square wave pulse generator will do a valid test. Pulse the coil at a low rep rate and when the square wave falls, count the oscillations that ring out to zero volts. 11 was always indicative of a good coil. Easier to just toss the one you have and get on ebay and buy another.......cheap.
 

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