bruker1 Posted June 21, 2019 Posted June 21, 2019 2004 Prestige, 23hp Command, 900 hours. First time this has ever happened. Mowing today at and when I hit heavy grass the mower bogged down and started running rough almost like the reverse sensor was trying to shut it down. Also a strong smell of gas while this is going on. Everything is serviced and well maintained. Any ideas?
SmilinSam Posted June 21, 2019 Posted June 21, 2019 Trying to flood out? Any signs of black smoke at the same time its running rough? I rarely have troubles with my Kohler carbs, but the 20hp briggs I swapped into my second Prestige was running rich, bogging down and not hardly eben running. Tried a carb kit first. Didnt help. New air filter helped some but not for long. Ended up getting a new carb and that fixed the problems.
bruker1 Posted June 21, 2019 Author Posted June 21, 2019 Nope, no black smoke. Runs fine except when it's working hard.
bruker1 Posted June 21, 2019 Author Posted June 21, 2019 OK, I think I figured it out. The left cylinder isn't firing. If I disconnect the right side plug wire and try to start it, it won't start. If I disconnect the left side plug wire and try to start it it will fire right up. I guess this would explain the lack of power and gas smell. I amazed how smooth it sounds with only one side firing. So what's my next step? Replace the coil?
jlasater Posted June 21, 2019 Posted June 21, 2019 Pull the plug on the left cylinder, hook up the plug wire, ground the base of the plug to the engine (insulate yourself), and spin the engine over to see if you get any spark at all. Could be a bad plug, bad plug wire, bad coil...start from cheapest and work your way back. 1
bruker1 Posted June 21, 2019 Author Posted June 21, 2019 ^Did that. The right side sparks both plugs, the left side doesn't spark either plug. Took the cover off and removed the coil/plug wire assembly. Looks fine but I'm guessing a bad coil isn't always obvious by looking at it? 2
bruker1 Posted June 22, 2019 Author Posted June 22, 2019 Back in business. I swapped a coil off of another mower and all's well. 2
jlasater Posted June 23, 2019 Posted June 23, 2019 Yeah...you can't tell from external appearances. The service manual may list resistance values for the coil, or you can probably find something online if you care to check (though replacing the coil is just as fast if you have one). Usually two terminals will show very very low resistance, the other two very high (primary and secondary). There's a great writeup here: https://www.yourmechanic.com/article/how-to-test-a-spark-plug-ignition-coil-by-eduardo-ruelas
PhanDad Posted June 23, 2019 Posted June 23, 2019 49 minutes ago, jlasater said: The service manual may list resistance values for the coil, Probably the same "faulty with age" ignition coil issue as the horizontal Command experiences. Here's a table from the repair manual listing resistance values: 1
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