No Spark On Briggs

raider820

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May 11, 2018
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I have a Cub Cadet Lawn Tractor with a Briggs and Stratton 18.5hp OHV engine, model number 31Q777 0305 E1 that has no spark. I have tried 3 different magnetos, the original, one from a tractor that I knew worked and a brand new one. Still no spark. I disconnected the kill wire while trying the second magneto and haven't connected it back up. The engine cranks over with no problems with the key and when I jump it straight from the starter, but I cannot get a spark. I have also checked to make sure the flywheel pin was not sheered and cleaned the flywheel magnet. I am at a loss. Can anyone help in determine why I can't get a spark?
 

Tinkerer200

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Mar 14, 2015
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How did you verify no spark?

Yeah, how? Just for the record, a sheared flywheel key will have no affect on whether it has spark, only affect if it is at the right time. (Unless it is a 1980 or older engine) Also, concern with corrosion, dirty, is only with the coil mounting surfaces.
Walt Conner
 

slomo

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Check the ground surface for the coil. Coils hardly go bad but possible. How did you set the coil gap? Verify the coil plates have a clean direct path to the engine block.

slomo
 

keakar

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Apr 28, 2020
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do this simple test, unplug the main plug to engine and then see if you have spark, if you do then its a safety switch somewhere killing it

its very common for the seat switch plug to back off a little and there is a spring wire in it that kills the mower thinking the switch is unplugged

note - if its still plugged in and the engine starts you need to plug it back in to kill it
 
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