How to Test an MTD Lawnmower

Slide the rubber boot at the end of the high tension lead wire slowly off of the spark plug, wiggling it back and forth, if necessary, to loosen it. Take off the boot and inspect the metal prong inside it for any damage or loose debris.

Unscrew the spark plug with a socket wrench. Take the old plug out of the cylinder and put a test plug into the boot, with the electrode facing out. Clip the test plug onto a secure, grounded metal point on the engine block.

Set the ignition to "On" if your lawnmower is so equipped. Open the throttle or choke lever to its normal "Run" position. Crank the starter rope or fire the ignition and check for a blue spark. A blue spark indicates a working ignition system. A yellow or no spark requires maintenance to the ignition system. Seek a professional to service the ignition for you.

Unhook the test plug from the rubber boot and ground the boot against a metal point. Screw a compression gauge into the spark plug hole finger-tight. Crank the starter until the gauge reading peaks then holds steady. The gauge should hold steady for your MTD mower. If the reading falls off or is under 50 PSI, have a mechanic check the compression levels.

Unscrew the air filter mounted to the side of the engine near the carburetor. Take the air filter box off of the engine. Unscrew the throttle plate in front of the carburetor and unhook the gas lines at the carburetor with your fingers. Gas should flow out of the lines. Check the entire fuel system if there is no fuel in the carburetor.