The process of troubleshooting requires some knowledge of the equipment. No technical skill or engineering degree is necessary, just a fundamental knowledge of critical components and their role in the mower's performance. Additionally, a logical series of steps, process of elimination and patience, will root out the cause of most Toro mower problems.
Check for spark when the mower does not start. After setting parked in the shed for a few days, or coming out of a long storage, a fouling or burnt spark plug is a common culprit. Remove the spark plug from the engine and hook the top of the plug into the cable. With the base of the spark plug touching the engine frame, turn the engine over for a second or two; a faint spark should appear the instant the engine starter engages. Replace the spark plug if no spark appears.
Check for stale or contaminated gas. Gasoline will drop out additives when stored for long periods of time. These additives contribute to gum and varnish in a carburetor. Moisture from condensation will also set up in a gas tank during the off-season. Drain the gas tank and replenish with fresh gasoline.
Inspect the gas vent if the mower starts and runs for a short time before it dies on its own. The gas cap contains a small vent hole allowing the tank to breath while fuel is siphoning to the tank. If trash or debris becomes lodged in the vent, the engine will choke down and die.
Inspect the battery connections for corrosion. Battery posts tend to corrode and reduce the ability for adequate current to flow to the starter. Remove the battery terminals and clean with a wire brush if corrosion is present. Lightly coat the battery posts with spray-oil before reinstalling the battery terminals.
Inspect the air filter if the engine runs rough or has a hard time idling smoothly. Without adequate air to mix with the fuel, combustion cannot occur. Remove the air filter and clean it with compressed air or soap and water. After washing, allow the filter to dry before reinstalling it into the breather.