"Mark Leininger" wrote in message
...
I have a craftsman lawn tractor with an 18HP Kohler twin, model M18S.
Twice now it has failed to start due to no spark.

WHEN there is no spark is the time to T/S. In the meantime, I'd locate a
wiring diagram and become familiar with it. OR (when the ignition is working
correctly) read it with a meter and draw your own diagram.


By the time I fiddle
with ignition switch and safety switch to see if something is not making
contact, it mysteriously starts.

Intermitant problems can drive you nuts.



I would say in my experience with other
small engines the spark intensity looks weak.
My question is about the ignition unit. Does anyone know if these are
prone to this type of intermittent failure as they get older (13 years)?
Is there some way to diagnose this other than stick a screwdriver in
the sparkplug wire to see if there's a visible spark?

I have device that is used to test the spark on outboard motors that may
help. It connects in place of the spark plug and has an adjustable gap for
the spark to jump across. Set to a wider gap than the normal spark plug gap,
an ignition system will produce a spark to jump the gap (passes the test) or
not (fails the test). I don't recall how much wider the 'test gap' will be
compared to the spark plug gap. At least it's more accurate (and safer) than
the 'screwdriver' spark test.

Larry