Kohler 17.5 won't start

This engine is on my lawn tractor, about 10 years old. Has been running great, cut lawn, shut off 3 or 4 times always, it started. Go to start 5th time, engine cranks fine but won't turnover. has good fuel, clean air filter.  used starter fluid in carb, still cranked but not even a small pop. Put a little gas in spark plug opening, same response, nothing, not even a small pop. Checked spark, white and orange, got new plug, no chnage battery at 12.80 volts. Disconnected ground form ignition module to eliminate any safety features preventing not starting, still the same. The spark is the same, white/orange if ground is connected or not nothing changes, just cranks.  Should my next try be replace the ignition controller at the flywheel, thinking its not working.