My Riding Mower Doesn't Have Any Spark

Spark Plug Wire

• A broken spark plug wire won’t transfer the voltage needed to provide spark. Since riding mower engines are different among the models, consult your operator's manual to identify where your spark plug and spark plug wire are on the engine. The average spark plug is grey with a white tip and has a wire leading to it. Examine your riding mower’s spark plug wire for any visible damage, especially where the wire meets the plug. This includes any signs of electrical arcing on the wire cover, usually identified by dark black marks.

Spark Plug Installation

• Spark plug installation isn’t just a matter of screwing it in until it’s tight. Spark plugs need a gap so that the electrode can properly fire. Over-tightening the spark plug can interfere with that gap or damage the spark plug. Under-tightening can shorten the spark’s reach to the fuel vapors and prevent combustion. Check your riding mower’s operation manual for the specific gap measurement.

Wet Foul

• If your riding mower is smoking heavily when you start it, chances are there is oil in your combustion chamber. While opening up the combustion chamber is possible, it is easier to check the spark plug itself. Examine the tip for a slick, oily cover. Oil in the chamber doesn’t combust and can end up covering the spark plug tip, fouling it out. Oil can leak in there if your riding mower has been tilted and oil spilled into the combustion chamber from the crank case. Other oil leak causes include worn oil rings, worn gaskets or plugged breather vales.

Choke System

• Some mowers have a choke control system on the throttle. This allows you to create a fuel-rich mixture for ignition in a cold engine. If the choke control is left open during operation, you can flood the combustion chamber with fuel. The spark plug will cold foul because it isn’t lighting. Cold fouling also happens if you leave your riding mower at idle too long.

Overheated Engine

• If the engine has overheated in the recent past, chances are it blistered the spark plug. Overheating happens if your riding mower’s cooling system has failed. Check for obstructions in the air cooling system, such as on the blower or cooling fins, which can prevent air from getting into the combustion chamber.