Engine Cub Cadet 1515 turns over but doesn't fire up

I have a Cub Cadet 1515 lawn tractor with a 15hp Kohler OHV engine purchased in 2002 that won't fire up. It has spark however I suspect that it is not getting fuel because the spark plug looks dry. I disconnected the fuel line from the carb and practically nothing came out. I lowered the gas line below the position of the gas tank and gas comes out. Since the gas line has a uphill travel to get to the carb, it there a vacuum that should occur that draws the gas to the carb ? Does anyone have any troubleshooting steps I could follow to isolate this problem ? Thanks