This engine is on a trail cutter. Never had a problem starting the engine before. The last time I used it all went well . 3-weeks later I went to use it again . Checked the gas and it was out. Filled the tank and did the usual start up procedure and it would not fire. Put a little gas directly in the carb and it ran for 3-seconds and stopped. Pulled some more , nothing. More gas in the carb and it runs till that gas is gone. Won't pick up gas. Any ideas.

You may have water in the fuel tank and carb bowl.