One possibility is that your fuel tank vent might be plugged or pinched. If the tank cannot vent properly, it could create a vacuum and prevent fuel from reaching the engine. Also, consider whether the engine might be flooded. If you’ve been cranking it a lot, it’s possible too much fuel has flooded the engine, which can prevent it from starting. You might want to let it sit for a while and then try starting it again. Additionally, check the spark plugs to make sure they’re not fouled. If there’s no spark, the engine won’t fire up.