Why does my lawn mower spark plug turn black?
Why does my lawn mower spark plug turn black? Black, dry soot on the electrodes and insulator tip indicates a carbon-fouled plug. This can be caused by a dirty air filter, excessive driving at low speeds, too rich of a fuel/air mixture or idling your vehicle for too long. What causes carbon build up on lawn mower spark plug? Carbon Buildup Carbon collects on the plug electrodes because of incomplete combustion. If the carburetor sprays too much fuel into the combustion chamber, the fuel burns cooler. The smoke that results fouls the plug as well as the air filter and...