It may be doing you a favor by not starting. First you'll need to make sure it's pumping fuel, and it's sounds like the tank need to be drained too. You can do both at once by pulling the supply line off at the tank and stick the hose into an apporved container. Then crank it over, if the pump works it will pump all the nasty shit out of the tank. If it ain't pumping fuel, I'm sure you'll know what to do next.