In alt.home.repair on Fri, 27 May 2005 14:05:49 -0000
(Chris Lewis) posted:

According to meirman :
Someone gave me a used push lawnmower with a Tecumseh 4-stroke engine.
It has no points or condensor under the fly wheel, so I assume that
means it has electronic ignition.

Is there a clear way to test the ignition coil/assembly to see if it
is good or not?

I get no spark, afaict, using an inline neon spark plug tester.

Am I correct in thinking that repairing the ignition coil assembly
will be next to impossible? And that buying a new one will cost more
than any push lawnmower that is probably 10 years old is worth?

I didn't have any trouble getting carb parts (in stock no less)
for a 6HP Tecumseh almost 40 years old. The parts were cheap.

Cool. That's the way I like it. I think Whirlpool washers are like
that.

You can test the coil yourself to a certain extent. Coils have
three leads, one of them being the spark plug wire. The resistance
between the two non-plug leads should be pretty low - a few ohms.
The resistance thru the spark plug lead to either of the other leads
will be fairly high, but not infinity.

This isn't a full test, but if it fails it, it's bad for sure.

Thanks. I think I did measure btween 2 or all three of them, but I've
forgotten the results. At the time I didn't know it could have
electronic ignition (even though I was wondering where the points
were. I'll check again.

A small engines repair place may well have a "proper" tester which
is capable of proving the coil good.

[Our small engines night course teacher has a "real tester". Got
to play with it last night.]

Repairing a truly dead ignition coil is virtually impossible.

One of the few things you can repair is cracked coatings on the
winding (_not_ the wire insulation, but the outer weather shield).
[make sure it's dry, and then coat it with RTV.]

OT, but I once had sparking from the diodes in my Amana microwave. It
was Model 2. The first person at Amana parts, when I only mentioned
the soudn of sparking, recommended a microwave tube. The next time he
suggested it was the diodes. They were a lot less money. When I took
the think apart, I saw the insulation on the wire was bad, and I just
covered it with black silicone cement. The thing worked fine for
another 10 years. Until the transformer failed.

Ignition coils aren't very expensive, you'll also find them
pretty universal between Tecumseh engines of even remotely similar
vintages. The link below says "These are just a few Tecumseh
Ignition/Electrical Parts".

http://willardssmallengines.com/shop...rts/page1.html
for example, lists several Tecumseh coils from about $25 to $45. A lawn mower
probably uses the cheap one.

I"ll check it out. Thanks

And thanks Lewis. Before electoronic ignition on cars, I was pretty
good at pulling plug wires off while the engine was running, without
losing control of my arm. But that skill may have been lost by now.
OTOH, maybe my nerves are near death by now.

Meirman
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