I have a 15.5 hp kohler engine craftman riding mower
It will crank over but has no spark at the plug unless you unplug the wire to the coil then you have spark any suggestions.
Thank you

Spark plug failed? Does it do this with different spark plug(s)?

Hi,
If you are speaking of the small wire that connects to the coil and leads into the harness, then you have something on the machine not associated with the engine grounding out the ignition. Could be seat, PTO(blade) or key switch.
Peace,
Clarke