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?

Meirman
--
If emailing, please let me know whether
or not you are posting the same letter.
Change domain to erols.com, if necessary.

I had a situation something like this recently, when I was repairing a
neighbor's lawn mower. It wouldn't start and I couldn't see a spark
from the plug.

What I did was to hold the plug in my hand and pull the rope.

It was _obvious_ that there was juice coming through. :-)

Lewis.

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.

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.

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.]

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.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.

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
--
If emailing, please let me know whether
or not you are posting the same letter.
Change domain to erols.com, if necessary.

On Fri, 27 May 2005 15:46:13 -0400, meirman
wrote:


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.



pull the kill wire off the coil and check for spark again, if
still none then it is the coil. resistance measurements are a waste
of time. isolate the component, then there is nothing else.
Chip

Meirman,

Its been a while since I replaced an ignition assembly on a
mower, but I recall that it is a very easy "remove and replace "
operation and the cost of the unit isn't too huge relative to the
cost of a mower.

Some random thoughts:
1) Check the electronic kill switch on the mower. Make
certain that your mower knows that you "want it to run."
Otherwise, you'll get no spark.
2) Make certain that you don't have a sheared woodruff key.
3) Check for proper gap between the magneto and the
flywheel magnet.
4) Test resistence readings on the ignition coil. This is
easy and very informative.
5) Examine, clean and/or replace the spark plug.
6) Test the coil output by inserting a nail into the spark wire
boot and then hold the other end of the nail near the block
while cranking the engine.
7) Test the spark plug outside of the engine by placing it
against the block and testing for spark. A plug will fire
more easily in the open than it will in the combustion
chamber. This helps determine if you are getting any
coil output.
8) Try temporarily reducing the spark gap to about 1/2 of
the factory spec. This makes it much easier to get a
spark from a less-than-perfect system. This is a good
diagnostic. Also, an engine can be run this way, although
it is a somewhat less than optimal situation. The smaller
spark impacts engine timing, but not in any destructive
manner. (to the best of my knowledge).

Good luck,
Gideon

================

meirman wrote in message ...
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?

Meirman
--
If emailing, please let me know whether
or not you are posting the same letter.
Change domain to erols.com, if necessary.

According to Gideon :

6) Test the coil output by inserting a nail into the spark wire
boot and then hold the other end of the nail near the block
while cranking the engine.
7) Test the spark plug outside of the engine by placing it
against the block and testing for spark. A plug will fire
more easily in the open than it will in the combustion
chamber. This helps determine if you are getting any
coil output.
8) Try temporarily reducing the spark gap to about 1/2 of
the factory spec. This makes it much easier to get a
spark from a less-than-perfect system. This is a good
diagnostic. Also, an engine can be run this way, although
it is a somewhat less than optimal situation. The smaller
spark impacts engine timing, but not in any destructive
manner. (to the best of my knowledge).

As a FYI, our "small engines instructor" says that the simplest
way to test for good ignition is to "construct" a 1/4" spark
gap, and you should get a reasonably fat/blue spark off it. Anything
less than that indicates you're probably not getting a healthy
enough spark, EVEN IF, you can see it on the much narrower spark
gap on a plug.

He "constructed" this tester by taking an ordinary plug, and sawing
off the threaded portion, leaving the center pin open on the end
of the ceramic insulator. Then, installed a clip on a wire
to ground it, and a screw to adjust the gap from the center pin
to the center pin. Install the modified plug into the spark
wire, the clip to a ground, and pull...
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.