Export thread

I hadn't fixed a small engine since early 70's. Back then it was a bad capacitor and you had to pull flywheel to get at it. So my honda gvc160 wouldn't start and I remember it being harder and harder to start last fall. My neighbor asked me if I could fix his Toro w/Tecumseh Eng. I figured it would be old gas and gummed up carbs. Replaced Ign. Coils instead and both start with half a pull and run like new. Now I'm just curious if its common for the mower to get harder and harder to start because the Coil is dieing a slow death? Also wonder about how long they usually last before burning out? Anyhow - pretty happy with such an easy fix. Thanks for all here who gave advice. Appreciated.

Hello,

They can die both way. I can't talk with experience of changing dozens of them, but even if you have a spark or even if a spark tester lights up this do not mean the spark is strong.

As you know, an ignition coil has two windings, one called primary that generate voltage with the magnet and a secondary to step up the voltage to an high value required for a spark at the plug. The last part is a trigger mechanism to release that spark at the exact right timing, more often integrated in what we call coils since about the 80's (if not you have points). More useful information here http://www.foxvalleykart.com/timing1.html

So about dying, if you have a problem with the trigger circuit it will die immediately.
You can have a cut in primary, or it is grounded, no more spark. A short of the output of secondary coil to ground no spark again.

But if you have a problem with windings isolation, it can go slowly, starting from shorting some portions (less turns = less voltage => weak spark) or working when cold but not hot for example. You can have cut in secondary and micro-sparks the bridge the gap, so again weak spark.
You can have the HV wire to the plug that has isolation degradation, again this eat energy before reaching spark plug. Or some moisture/path somewhere in secondary coil that has the same result.

As you can see, many way to fail - even if it is a reliable part on on small engine, we see often way more problems with carbs

Thanks for detailed response. I replaced the lamination yesterday and mowed for an hour or so. Never died or stalled. Seems like engine still harder to start after it has run awhile. Tends to rotate quite a few times using electric start then it backfires once and starts and runs normal after that. While mowing it sounds good and seems to have plenty of power.

I noticed the "carbon" canister thing when I removed the cowling to replace the lamination. Could that cause any issues with how engine runs if its dirty. Seems like it shouldn't wear out after 2 years? Its a 2017 model.

Meanwhile my oldest mower a Craftsman with Honda engine (Honda Logo At Least) fires up on 2nd pull after sitting all winter with old gas in it. Frustrating that this 2 year old Toro doesn't run better.