How To Check The Condition Of The Spark Plug?

In addition to the sealed ignition test with special instruments, the technical status of the spark plug can also be checked by the following methods.
(1) On-vehicle inspection method
a. Touching method: Start the engine, let it run at idle speed, and touch the insulating ceramic part of the spark plug with your hands. If the temperature rises very high and quickly, it indicates that the spark plug is normal, otherwise it is abnormal.
b. Short-circuit method: Start the engine and let it run at idle speed, then use a screwdriver to short-circuit the spark plug cylinder by cylinder, listen to the changes in engine speed and sound, if the speed and sound change obviously, it indicates that the spark plug is normal, otherwise it is abnormal.
c. Flashover method: Unscrew the spark plug, place it on the cylinder block, and test the fire with a high-voltage line. If there is no spark or the spark is weak, it means that the spark plug is leaking or not working.
(2) Appreciation method
Remove the spark plug and observe, if it is reddish brown or rusty, it indicates that the spark plug is normal; if it is oily, it indicates that the gap of the spark plug is out of balance or the oil supply is too much, the high-voltage line is short-circuited or disconnected; if it is smoky black, it indicates that the hot and cold type of the spark plug is wrong. Or the mixed gas is thick, and the engine oil is running up; if there is deposit between the top and the electrode, when it is oily deposit, it means that the cylinder blowing engine oil has nothing to do with the spark plug. In the case of gray deposits, it is the additives in gasoline that cover the electrodes and cause misfire; if the ablation is severe, such as scarring on the top, black pattern cracks, and electrode melting, it indicates that the spark plug is damaged.