12 HP Kohler/ Gravely No *Spark*

Ok I went to start my 8122 Gravely Tractor today and it would not start. To make a long story short it has no spark in it's 12 HP Kohler Engine. I'm not real familiar with these small tractors but,I started to check the obvious.

Things I've checked.

1. Battery is strong. 12.7 volts on meter and is cranking the engine fine.
2. I have power to the coil.
3. I have power to the points (They have the correct gap)and I have a nice blue spark between he points when cranking.

Now the mystery:

1. With a spark tester in the coil I get no spark what so ever.. Can a coil be bad yet still allow spark at the points?
2. From reading the manual I discovered this engine does not have a magneto,but it has a stater. I assume that is just for the charging system? Or does it have something to do with the spark/running as well?

A coil can short out and have power into and out of it but yet not make a spark No common but it can happen. If you happen to have a coil laying around form some other engine you can wire it up and try it out.

With the primary ignition circuit working correctly, the problem is likely the coil. If the coil wire can be inspected carefully to be certain it is not broken, or cracked, Replace the coil. Jim

Ok thanks!! Thats what I was thinking possibly

Ok thanks!! I think I have a extra one laying around

Is the coil bolted to the engine? If it is, engine vibrations have probably shaken it apart. Two of my single cylinder Kohlers ate coils until I relocated the coil to somewhere on the garden tractor frame where it was isolated from the engine.

Jason, good questions, let me take a shot at it:

1. Battery is strong. 12.7 volts on meter and is cranking the engine fine.
2. I have power to the coil.
3. I have power to the points (They have the correct gap)and I have a nice blue spark between the points when cranking.

Having power TO THE POINTS tells me the coils LV Primary at least has continuity and the voltage applied to the coils input is getting to and is present on its LV output SO FAR SO GOOD.

YES the points will spark a bit when opened because when the coils current is interrupted voltage rises and a small current may arc the gap and again that tells me the coils LV primary is intact. The condensor is there to buffer that to some extent by absorbing some of the energy so the points dont burn prematurely.

I would put a test lamp on the coils output (to points) and turn the engine over and insure the light shines bright when the points are open, but goes COMPLETELY OFF when closed. If it doesnt go completely off (maybe dims) when the points are closed, they are burned or carboned or pitted or not closing fully and you will get no or a weak spark. If the light never comes on when the points are open, the condensor may be shorted or theres a wiring short or the coils LV primary is bad open.

I would next connect a spark plug (its frame grounded) to the coils top HV output wire and turn on ignition and each time the poinst are closed but then open, IF THE COIL IS GOOD IT SHOULD FIRE THE PLUG. Another test is to remove the coils output to the points so you eliminate any problems there and use a jumper wire there (coils output to points) and momentarily connect and remove the jumper to frame ground to see if the plug fires each time its connected but then removed?????? If the coil NEVER fires the plug regardless if a jumper or the points are used to make and break the frame ground connection THE COIL MUST BE BAD


Now the mystery:

1. With a spark tester in the coil I get no spark what so ever.. Can a coil be bad yet still allow spark at the points?

ANSWER YES the LV primary can be closed and continuous BUT THE HV SECONDARY CAN BE OPEN OR BAD OR THERES HV BREAKDOWN


2. From reading the manual I discovered this engine does not have a magneto,but it has a stater. I assume that is just for the charging system? Or does it have something to do with the spark/running as well?

Its typical to have magnets on the flywheel (Rotor) that induces voltage into the Stator windings for charging the battery, but that has nothing to do with the battery powered coil points ignition.

Some engines use a MAGNETO ignition that doesnt require battery power, but you talk about yours being a battery powered coil ignition.

Run the checks above but if the coil never fires using a jumper nor will it fire with a good set of points, ASSUMING THE CONDENSOR IS OKAY, Id try another coil.

John T Post back any questions

Thanks for the tips! I have off all week so I'll mess with it. I put new points and condenser last year in it but that doesn't mean much in this Chinese word.

Yes it's mounted on the engine. It's
been there a while I've never changed it
since I've owned it. It may have just
ran it's course but thanks for the info
I'll keep it in mind.