Murray Riding Mower: No Spark

[Oliver]

Disappointing weekend:

Have a 18.5hp, 46" Rider from Murray. Model 46570x8A Ran it till it was completely out of gas. Filled it back up, and tried to start it. Repeatedly. Engine turns over fine, but doesn't catch. Tried till the battery needed a jump start. (Took breaks to keep from hurting the starter.)

2 Days later and can still not get it started.

Debug steps tried so far:

1) Checked under air filter, saw gas squirting into the carb. Also noticed gas smell from exhaust, while I was trying to start engine. So, seems to be getting gas. Engine turns over fine, just doesn't catch. 2) Pulled a spark plug, and rested it on the engine block. Did not see a spark. 3) Replaced both spark plugs. Still do not get a spark. 4) Confirmed that yellow grounding wire that connects to the Armature is *not* connected to ground, as long as I either have the brake pedal down, or the seat switch depressed. 5) Ohm'd out the diode in the red wire that runs from the ignition switch to the Stator. Looked good. 6) Checked the fuse. Ok. 7) Replaced Ignition Switch. Still doesn't get spark. 8) ... help?!! There's not much left.

I'm looking at the "Parts List" book that came with the mower. Has an Electrical System diagram, and I have to admit, I'm having trouble seeing the current flow path that ultimately supplies battery power to the spark plugs. Of course, I'm not really sure of what a Stator does, so that's probably the problem. Seems like the Stator and the Armature are the only things left.

What (how) do I check next???

Thanks!

-Oliver Raleigh, NC

[bumtracks]

Not familiar with your mower/engine combo but most small engines/spark plugs are non-battery powered magneto - alternator charging coils/magnets under and built into the flywheel - magnets passing the coil(s) juice it to fire - probably one spark each revolution. Extra wasted spark at exhaust tdc. battery just turns the starter, powers headlights, maybe an electric clutch, guages, etc.

Sounds like you're hip on wiring, maybe put an ohm meter on all your safety switches make sure they open/close - perhaps a rat or squirrel chewed through a wire? ground path is shorted ?

gardenweb.com has riding mower forum with a few experts.

[m Ransley]

Ignition module ,or coil , or seat or other saftey switch or bad wire.

[Oliver]

It was the coil (armature).

Replaced the coil, gapped it with a business card (when the coil and stator magnets pulled together), and it cranked right up.

Thanks for the help.

-Oliver