Loss of Fuel

• The fuel system operates in a closed loop through the vacuum pressure created by the pumping crankcase. It originates in the tank, travels to the carburetor, where the necessary amount is sent off for combustion, while any remaining fuel gets sent back to the tank. At any point along this circuit the gas flow may get impeded, and when it does, the mower will stall. Common points of obstruction occur at the fuel filter, in the fuel hoses, at the carburetor’s intake and inside the carburetor.
  
  

Loss of Air

• The engine on a Craftsman lawn mower needs to breath much like a human. The engine sucks air in, to mix with the fuel, and vents used up gases away from the engine. Air enters the engine and gets cleaned at the air filter. Air gets blown away from the engine at the muffler. If either of these points gets obstructed the engine will stall and shut off. Common obstructions occur with a dirty air filter or a clogged spark arrestor screen.
  
  

Loss of Spark

• After the fuel gets mixed with air, it gets sent to the combustion chamber. A spark plug emits a high-voltage spark, igniting the fuel and powering the piston and the crankcase. After repeated uses, the spark plug’s tip will gradually build a coating of leftover burnt gases. These gases will eventually restrict the charge and the mower will start, but quickly stall again. Other issues, which a professional should address, occur at the battery, in the ignition wires and at the ignition module.
  
  

More Serious Complications

• The fuel, air, and spark manage to keep running on their own through the vacuum pressure caused by the explosion of the fuel and the movement of the crankshaft. This compression pushes the fuel to the carburetor, spins the flywheel to generate the spark and causes the engine’s fan to suck in more air. A loss in this compression will cause the mower to stall. Compression loss usually occurs when air leaks into the internal portion of the engine.