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I have a Snapper 21356B push lawn mower and the engine won't start. It's a Briggs and Stratton 121700 (3.5 HP). I determined there is no spark so I tried a new plug - nothing. I don't know a whole lot but did some research, and decided to try and clean the points. I took the flywheel off but can't figure out where they are located, and can't see anything that resembles a condenser.






Maybe I'm going about this the wrong way. Is there a way to check the ignition coil and see if it can make a spark? I don't know which order to check things in, and at this point I'm stuck. Any help would be appreciated.

Brian

first thing is you dont have points so what you need to do is put the flywheel back on pull the kill wire off of the coil and see if you have spark then if so you have a kill wire grounded if not you have a bad coil good luck

Thanks for the reply. So are you saying I should disconnect the kill wire from wherever it is connected on the mower, then put everything back together, then check for spark again? If I have spark, what do I need to do with it?

Puls.bm said:

Thanks for the reply. So are you saying I should disconnect the kill wire from wherever it is connected on the mower, then put everything back together, then check for spark again? If I have spark, what do I need to do with it?

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If you have spark remove the spark plug an put a little bit of gas in and reinstalled the plug and see if it runs a bit.

Puls.bm said:

Thanks for the reply. So are you saying I should disconnect the kill wire from wherever it is connected on the mower, then put everything back together, then check for spark again? If I have spark, what do I need to do with it?

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If removing the kill wire allows spark, then there is a short on that kill wire. Somewhere the wire is grounding out constantly. It is only supposed to ground when you shut the engine off. But you may have other issues. Remove the coil and clean any and all rust off where it contacts the block, and where the magnets on the flywheel pass it. Clean the magnets as well. When reassembling, use a 3X5 index card as a spacer between the magnets and the coil to get the gap right.

Thanks for all the help. I disconnected the kill wire from where it was connected, reassembled the engine, and cleaned/tightened the spark wire where it connects to the plug to make sure there was a good connection there. Tried turning it over while looking for a spark in the gap and saw nothing. I will try what you said, clean off the ignition parts and magnets. Should I use a fine sandpaper to do so, or just a damp rag and some elbow grease? If that doesn't work, I think I can conclude that it is a bad ignition coil, right?

u need a new coil

I cleaned the coil first in soapy water, then with steel wool to get the rust off. Then I cleaned the magnets lightly with the steel wool. I put everything back together, used a business card for the gaps, and tried it out. No spark. Can I safely conclude that I need a new coil?

Puls.bm said:

I cleaned the coil first in soapy water, then with steel wool to get the rust off. Then I cleaned the magnets lightly with the steel wool. I put everything back together, used a business card for the gaps, and tried it out. No spark. Can I safely conclude that I need a new coil?

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Never clean a coil in soapy water.

if you completley isolated coil from kill wire and still no spark new plug you need a coil