Can't start lawnmower, as it's getting no gsoline. Gas comes thru the fuel line real good where the line runs through down low at the back of the engine, but when I run it back up to the carb to reconnect the line, no gasoline comes out the fuel line. The line isn't clogged, or it wouldn't be coming out at all. I cleaned the fuel filter. Any suggestions on what the problem is? This is a 2 year old Craftsman lawnmower.