How to Distinguish Between Good and Bad Spark Plugs?
1 Answers
Methods to distinguish between good and bad spark plugs are: 1. If the spark plug is blackened as if smoked, it indicates that the cold/hot type of the spark plug was incorrectly selected, the air-fuel mixture is too rich, or engine oil is seeping up. If the spark plug is reddish-brown or rust-colored, it indicates the spark plug is normal; 2. If the spark plug is severely eroded, with scarring, black streaks, cracks, or melted electrodes at the top, it indicates the spark plug is damaged and must be replaced immediately; 3. Let the engine idle and listen carefully for changes in engine speed and sound. Obvious changes in speed and sound indicate the spark plug is normal, while insignificant changes indicate the spark plug is in an abnormal state; 4. Unscrew the spark plug and place it on the engine block, then test for spark with a high-voltage wire. If there is no spark or the spark is weak, it indicates the spark plug is leaking electricity or not working.