Over time, certain ingredients in the fuel used to run the snowblower can evaporate, leaving behind a thicker stickier substance. This substance can create a restriction in the carburetor which can cause the engine to stall after it starts. You can try cleaning the carburetor with carburetor cleaner to eliminate the clog. If cleaning is not effective, you can often purchase a carburetor rebuild kit to replace some of the components or install a new carburetor altogether.
02 - Clogged fuel cap
As the fuel is consumed, the level in the fuel tank lowers. To make up for this, fuel caps have small vent holes to allow air into the tank. If the vent holes are blocked by build-up or debris, air will not be able to enter the tank, creating a vacuum that will cause the engine to stall. You can replace the fuel cap with a new one to solve this problem.
03 - Defective spark plug
Due to carbon buildup and a weakened electrode, the spark plug will degrade over time, which can cause the engine to stall. You should inspect the spark plug for damage or wear, you can also use an ignition tester to help determine if the spark plug is defective. As a general guideline, you need to replace the spark plug with a new one once a year.