Toro self propelled lawn mower ignition problem

[Jeff Liebermann]

On Thu, 6 Sep 2012 05:08:32 -0700 (PDT), klem kedidelhopper
<captainvideo462009@gmail.com> wrote:

The second one
happened to mention that you should never fire an ignition coil with
the secondary disconnected from the spark plug or as they put it a
"suitable load". The article went on to say that doing so could cause
internal acing in the coil and damage it. I never knew this but it
makes sense and incidentally adds up as well. I happened to mention
this to my son this morning and he admitted that during the course of
his working on the engine when he had it running for a few seconds and
then it would die he had done this very thing.

90% baloney as usual. There are two ways to "run" an engine without a
load on the ignition coil.

One is to hand start the engine with the spark plug wire disconnected.
That won't do any damage as there's not enough energy in the spark
from hand cranking to do any damage.

The other way is to run the engine for a while, and remove the spark
plug wire. Assuming you can do this without getting a nasty shock, it
might internally arc across the coil. However, in my limited
experience with chain saws and small generator engines, a shorted coil
will still generate a small arc. Not a hot or big as a normal coil,
but unless the short is somehow across the entire coil (easily found
with an ohmmeter test), you'll still see a tiny spark. Buy a real
tester:
<http://www.ebay.com/sch/i.html?_trksid=p5197.m570.l1313&_nkw=spark+plug+tester>
(I made my own spark gap from a piece of U shaped plastic).

What I think happened here is that someone transplanted the story from
their automobile or multi-cylinder engine experience. With more than
one cyclinder, it is possible to run the engine with one spark plug
wire disconnected, which might cause internal arcing. However, it's
not likely with a single cylinder engine.

Note that the coil part number that I excavated is used in Husqvarna,
Tecumseh, Toro, and others. If it was as failure prone when NOT
running as you imply, there would be recalls and other failures in
epidemic numbers.

Testing the ignition:
<http://www.youtube.com/watch?v=MNvwZmZj610>

This one covers most ways to test your engine spark.
<http://www.youtube.com/watch?v=5qSgmunp_Ys>

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[bw]

"Bob Engelhardt" <bobengelhardt@comcast.net> wrote in message
news:k2ahcq01974@news7.newsguy.com...

Pat wrote:
I'd be convinced by an actual case of an internal arc - anybody ever see
one?

Bob

Yes. Many. Thats how they fail. Temperature, vibration, aging induce small
cracks in the insulation. Dirt, moisture infiltrate, etc. Better coils are
designed with internal aux gaps greater than the normal spark plug gap. I've
dissected failed coils, not hard to find traces of internal arcing, melting.

 

[Jon Elson]

Bob Engelhardt wrote:

I'd be convinced by an actual case of an internal arc - anybody ever see
one?
Well, I had a B&S engine that would run for 10 minutes or so, and then

get weak, sputter and finally die. if you let it sit for a couple
minutes, it would start and run for 30 seconds or so and die again.
A new spark coil fixed it completely, and it ran fine until the deck,
wheel drive, etc. was completely worn out.

Just had a problem with its replacement mower. it would run for about
20 minutes, start knocking, lose power and then die with a big blast of
oil smoke, I guess it got hot enough to boil the oil out the crankcase
vent, and sucked that into the carb. I cleaned the cooling passages,
but that didn't help. It finally occurred to me the timing could be off,
so I checked the shearable key on the flywheel, and it was sheared.
I haven't run it for 20 minutes yet, but I'll be that was the problem,
advanced spark timing. It does seem to run better though, I'll put the kids
to work soon for a more exhaustive test of my repair.

Jon

 

Replace the coil and be done
Jerry

 

[Allodoxaphobia]

On Fri, 27 Feb 2015 09:08:17 -0800 (PST), digulla5@gmail.com wrote:

Replace the coil and be done
Jerry

HUH? I don't even own a Toro self propelled lawn mower!

Oh, I see... Another google grooper...