Why Does My Toro Lawn Mower Shut Off?

Air

• The fuel inside the Toro lawn mower is too concentrated to ignite at a temperature high enough to keep the piston and crankcase moving. The fuel, therefore, needs dilution with air. Air reaches in the engine, via the air filter, where it gets mixed with the fuel inside the carburetor. Air escapes the engine via the muffler. If either of these ports gets restricted, the loss of air usually results in an engine that shuts off. Wash the air filter in soapy water and rinse under cool water, letting it dry thoroughly. Scrub out the muffler and spark arrestor screen.

Fuel

• Fuel moves in a continuous circuit from the tank to the carburetor to the cylinder and back to the tank, if it's unused. Like air, fuel needs to move continuously, and any stoppage of fuel will translate into an engine shutdown. Even small losses of fuel can cause surges, rough idling and stoppages. Work from the fuel tank through the entire fuel system, moving up to the carburetor. Clean all fuel passages and replace any parts too dirty to clean. Allow a professional to service the carburetor.

Spark

• When the fuel, diluted with air, reaches the cylinder a short burst of high voltage electricity discharges, thus igniting the fuel. This spark travels from the ignition module up the lead wire and to the tip of the spark plug. Again, any loss in the spark or resistance to the current will cause the engine to shut off. Change the spark plug at least every season. Due to the dangers of electrocution, allow a service professional to operate on other parts inside the electrical system.

Compression

• For these three elements to continue working in conjunction with one another, the engine needs to remain in a vacuum. This pressure allows the fuel to pulse in time with the crankcase and any drop in the pressure inside the engine can cause serious engine problems. Compression losses occur due to an influx of air somewhere, most often, in the crankcase or cylinder. Compression issues, like other major engine parts, will need a service professional to address and fix.