Spark Plug Test

Remove the spark plug and connect to the ignition coil.

Fig 1: Removing Spark Plug And Connect To Ignition Coil
Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
Ground the spark plug outer electrode (body), and crank the engine.
Check that there is an electrical discharge between the electrodes at this time.

Fig 2: Checking That There Is An Electrical Discharge Between Electrodes At This Time
Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.