So we are talking about a Kohler M18 twin cylinder. It has one coil for both cylinders which fires on every revolution of the engine. Very simple coil 2 secondary wires to the plugs and a kill wire. Kill wire go's to ground and the engine loses spark and the engine turns off, very simple. Have these problem's just started? You also said it also is dieseling and wouldn't start when cold. Seeing it not a stock engine who wired it and is it wired right. Does the engine have a good ground? Are the battery cables the right cables and are good?