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I have an MTD riding mower with a 20hp Tecumseh engine. The engine quit on me yesterday while I was mowing, and I'm at a loss as the problem. I have ignition spark on both cylinders. (just installed new plugs). I soaked the carbs in carb cleaner and checked all the air and fuel ports. I verified that the fuel pump is getting fuel to both carbs. Strangely, the engine won't even fire when ether is sprayed in the carbs - even directly into the plug port, it won't fire. I pulled the flywheel and verified that the timing key is ok. I'm thinking that this has to be a either a lack of air problem or the magnetos are not producing enough voltage for a sufficient spark. I checked the spark with a light tester and also pulled the plugs and verified that there was a visible spark between the electrodes and ground. Has anyone else has a similar experience or does someone have any clue as the the problem ?

Marlo235 said:

I have an MTD riding mower with a 20hp Tecumseh engine. The engine quit on me yesterday while I was mowing, and I'm at a loss as the problem. I have ignition spark on both cylinders. (just installed new plugs). I soaked the carbs in carb cleaner and checked all the air and fuel ports. I verified that the fuel pump is getting fuel to both carbs. Strangely, the engine won't even fire when ether is sprayed in the carbs - even directly into the plug port, it won't fire. I pulled the flywheel and verified that the timing key is ok. I'm thinking that this has to be a either a lack of air problem or the magnetos are not producing enough voltage for a sufficient spark. I checked the spark with a light tester and also pulled the plugs and verified that there was a visible spark between the electrodes and ground. Has anyone else has a similar experience or does someone have any clue as the the problem ?

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You can do all you mentioned and if you're not getting sufficient compression, the engine will not run or will not run enough to pull anything if you're lucky enough to get it going. Doesn't make sense for an engine to quit suddenly due to lack of compression, that's usually a gradual thing. Have you done a compression check? Just hold your thumb over the spark plug hole and crank the engine, should be enough compression to blow your thumb off the hole. If the compression is good, then it seems to me you're grounding out somewhere with the ignition kill wire, something in the key/switch unit, or perhaps a safety switch making it die. When you said it died suddenly while mowing, that makes me want to look for an electrical problem, maybe an intermittent kill wire grounding out some place. Did you have a helper sitting on the mower cranking it over while you looked for spark? Hope this helps narrow it down some.

Yes, my wife cranked the thing while I observed the spark. Curiously, grounding out is what I initially suspected, but can I still get an ignition spark with a a short to ground ?

I got a snapper zero turn given to me that wouldnt run. i checked the wiring after i went through the usual stuff(carb, plugs, etc). i got it to run, and was trying it out and it quit on me. i checked some of the safety interlock switches, and found two of them bad. it would start right up after it cooled down a bit, but run it for 5 minutes and it died again due to the safety switches and a rough edge that rub against the wire causing it to short out