George Wrote:
> On Sat, 9 Sep 2006 05:37:25 -0700, jeffcoslacker
> > wrote:
>
> >
> >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...
>
> This is a 7 hp pull start, and it has some sort of compression relief
> to
> reduce the starting effort. It works off the crankshaft speed. I
> figured it out once, but I don't remember the details.
>
> G
See if it will start with a dry plug and the air cleaner removed.
Let me know.
I did see Kohler has a compression release, I was wondering if you
figured that into the compression reading...
Your spark, fat and blue or thin and yellow/white?
--
jeffcoslacker
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