George Wrote:
> I have an old tiller with a Kohler single-cylinder 4-stroke engine. It
> lost all power (over about 30 secs), and now won't start. Since then,
>
> - Replaced spark plug. (Which does spark, when grounded to the
> head.)
>
> - Points look OK.
>
> - Compression looks OK (75 psi).
>
> - Cylinder is getting fuel (plug gets wet, and exhaust smells.)
>
> - Carb float valve works, and float seems OK.
>
> - Coil resistances look OK.
>
> - I cranked it in the dark, and didn't see or hear anything bad
> around the coil.
>
> I wonder if I have a weak spark when the plug is installed. But, a new
> coil costs $75, which is a kind of expensive experiment.
>
> To test the coil, I made a 10:1 voltage divider (with a HV 10M
> resistor), and looked at the spark plug voltage with a scope. With the
> plug not grounded, I see a 4-6KV pulse. When the plug is grounded, this
> drops to about 1KV. I get the same 1KV when the plug is in the cylinder
> (no fuel).
>
> Questions:
> - Is above consistent with a 'weak' coil?
> - Is there another way to test that?
>
>
> And, any other thoughts would be appreciated.
>
> G

75 psi compression doesn't sound like enough for a gas engine to
run....usually around twice that...


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jeffcoslacker
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