What to Do If a Yard-Man Self-Propelled Lawn Mower Won't Start

Check Spark Plug

• A lawn mower's ignition system delivers the necessary high voltage charge for the internal combustion engine. When the lawn mower's spark plug can't deliver a full high-energy blue arc, the fuel will ignite at lower temperatures. This will decrease the consumption of fuel, leaving the deposits behind through the engine and carburetor. After removing the spark plug from the engine, replace the plug if the tip looks blackened or bent in any way. Screw the new plug in and try restarting the lawn mower.

Test For Spark

• If a spark is getting lost before the plug, the engine will not start at all. Test the spark plug against the cylinder for a strong blue arc. Insert the spark plug, electrode facing out, into the rubber boot at the end of the high-tension lead wire. While wearing leather work gloves, hold the wire just below the boot, and the tip of the spark plug about 1 inch from a grounded metal point on the engine block. Crank on the starter rope. If a blue spark jumps across the point the trouble lies in another system. Perform further troubleshooting and repairs to the ignition system as necessary.

Check for Fuel

• If the lawn mower's getting a spark, check the engine for a sufficient supply of fuel and oil. Gas in the lawn mowers leave behind trace elements, which break down plastic parts, like the hose, tank and carburetor. Use only fresh fuel in lawn mowers and buy only what you can use in a 30-day period, as the gas will begin destabilizing, leaving behind even more fuel deposits in the engine. Check the quantity of oil in the crankcase and add more SAE 30 weight oil if necessary.

Compression Issues

• Starting issues can also involve parts farther into the interior of the engine. These issues will eventually manifest as a mower that won't start and be difficult to crank or turn over. Loss of compression usually occurs around the crankcase seals, making it difficult to diagnose. Use a compression gauge to test the level in the engine if you suspect a loss in compression. Allow a professional to service and repair compression related issues.