I have a Snapper lawn tractor with an 18hp Briggs and stratton Vanguard motor. It was running rough when i parked it for the winter. Now i try to start it and it cranks but wont start. It will run on carb cleaner if i spray it when cranking but dies out as soon as i stop spraying. I figured it was the fuel pump.Changed it with all the lines and filter but still nothing. I verified that it is pumpimng fuel to the carb inlet. Any ideas? I thought maybe the float was stuck open but the plugs are clean.