How to Determine the Condition of Spark Plugs?
2 Answers
Methods to determine the condition of spark plugs: 1. Short-circuit test: Let the engine idle, and use a screwdriver to short-circuit each spark plug one by one. Carefully listen to changes in engine speed and sound. If the changes in speed and sound are obvious, it indicates the spark plug is normal; if the changes are not obvious, it indicates the spark plug is abnormal. 2. Spark test: Unscrew the spark plug and place it on the cylinder block. Use a high-voltage wire to test for spark. If there is no spark or a weak spark, it indicates the spark plug is leaking or not working. 3. Visual inspection: Remove the spark plug and observe its appearance and color. If it is reddish-brown or rust-colored, it indicates the spark plug is normal; if it is oily, it indicates the spark plug gap is misadjusted or there is excessive fuel supply, or the high-voltage wire is short-circuited or open-circuited; if it is black as if smoked, it indicates the wrong heat range was selected for the spark plug or the mixture is too rich, or engine oil is leaking into the combustion chamber.
Judging the condition of spark plugs is actually quite simple. First, examine the removed electrode section. In a healthy state, the ceramic insulator should appear grayish-white or light brown. If you find severe carbon buildup turning it black, that indicates issues like an overly rich fuel mixture or oil burning. The electrode gap is also crucial—measure it with a feeler gauge. For most family cars, the ideal gap is between 0.8-1.2 mm; if it's too large or too small, replacement is needed. Remember to check the metal shell threads for any signs of gas leakage or cracks, as these are potential hazards. Finally, observe the combustion condition—if the electrode shows severe erosion with rounded edges or a missing tip, it means the spark plug has reached the end of its lifespan. I recommend checking them every 30,000 to 50,000 kilometers; don't wait until the car starts idling roughly to take action.
