The Eyes Have It

• Make a detailed visual inspection of the push mower. Check the fuel supply in the tank for water contamination, or lack of fuel. Make sure the filler cap vents are clean and unobstructed. Inspect the fuel filter, if the mower is equipped with one, and clean or replace any suspect parts. Rubber fuel lines should be firm to the touch, with no kinks or sharp bends. Safety switches should operate smoothly and completely, with no binding or interference from adjacent parts.
  
  

Testing the Fuel Supply

• Any discrepancies noted in the fuel tank may have affected the carburetor. Remove the air filter and spray a one-second blast of aerosol carburetor cleaner down the carburetor "throat." Attempt to start the mower. If it runs for a few seconds and stalls, the carburetor should be taken apart and cleaned. To conduct this test without carburetor cleaner, remove the spark plug and pour 1 tsp. of fresh fuel into the spark plug hole. Replace the plug to test-start the mower.
  
  

Ignition Tests

• A dirty air filter can cause the engine to flood, and prevent ignition. Replace the air filter, or clean and reinstall the old one. Remove the spark plug and inspect the "business end" of the plug. Liquid fuel found on the electrodes indicates flooding, and the plug should be replaced. Also replace the spark plug if heavy buildup or damage is evident. Set the spark plug gap to manufacturer's specifications, and test-start the mower.
  
  

Engine Functions

• Check the ignition system by installing a spark tester in between the plug wire and plug, and turning the engine. System component failure is indicated by a lack of spark. This test method keeps sparks contained and away from fuel system components. Test engine function with an engine compression gauge made to thread into the spark plug hole. Note the gauge readings while turning the engine over. Any readings below the manufacturer specifications indicate internal engine problems. In either case, professional assistance may be required.