With that much fuel, the only other place to look is ignition. You advise the engine is spinning over so the "Safety Interlocks" are not malfunctioning. If it is a Kohler engine, Kohler usually uses a white wire to ground the coils. Remove the plugs, attach a spark plug wire to one of the plugs and then use a pair of vise grips to hold the plug to a metal ground. I use a piece of covered wire, attach one end to a good ground on the mower (ground post on battery) and then attach the other end to the spark plug with he vise grips. Used to just hold the ignition cable. Some of the mowers today put out quite a wallop. Spin the engine over any spark at the gap on the spark plug?
No spark check and see if you can see a white wire coming out of the covering on the engine. Trace the wire to a point where you can disconnect and see if the engine will starts. If the engine starts you will have to ground the white wire to stop it.
The ignition switch could also be shorting the start circuit to ground when turned to the start position.
Turn the ignition switch to the on position and jump the solenoid at the starter and see if the engine will start.
If the coils have gone bad, call the dealer. Removing the sheet metal to get to the coils can become rather involved.
While you have the plugs out, do the thumb test. Place your thumb or other finger in the spark plug hole and spin the engine over. Got good compression, blow out and suck in on each cylinder? If not you have a valve train problem.
