[Bill in SoCal]

My guess is that gas is draining down the intake manifold and past the cylinder rings when the engine is turned off. Bad float valve or too much pressure from the pump. Does the pump start pumping when the ignition is on before starting the engine? If it does stop pumping - will it start again in a few minutes with the engine still off?

Gas washes the oil of the cylinder walls and thins the oil which will cause more than normal wear on all the engine parts. The more gas the more wear. Bill