How to Determine the Condition of Spark Plugs?
2 Answers
Determining the condition of spark plugs: 1. Short-circuit method: With the engine running at low speed, use a screwdriver to short-circuit between the high-voltage wire of the tested spark plug and the cylinder block, cutting off the spark plug's operation. If the engine speed significantly decreases and shakes, it indicates the spark plug is functioning well; otherwise, it is malfunctioning. 2. Temperature sensing method: After the engine reaches normal operating temperature, touch the ceramic body of each spark plug by hand. If a spark plug feels cooler, it can be judged as malfunctioning. 3. Spark gap method: Remove the high-voltage wire from the spark plug, maintaining a 5mm gap between the wire end and the spark plug terminal. If the engine's performance improves, it indicates a fault with that spark plug.
To determine the quality of a spark plug, I personally start by removing it and carefully inspecting its appearance. The electrode gap is crucial, typically around 0.8 to 1.0 millimeters—measure it with a feeler gauge, as gaps that are too large or too small are problematic. Next, check for carbon deposits: if the center electrode has dry, black deposits, it often indicates a rich fuel mixture; if it appears white or grayish-white, the engine might be overheating; oily deposits usually point to an oil leakage issue. The condition of electrode wear is vital—rounded or severely eroded tips mean it's time for a replacement. Cracks in the insulator or heat cracks are absolutely unacceptable. New spark plugs have sharp electrodes and uniform color, making it easy to compare and assess their condition. Regular checks can also prevent engine misfires or increased fuel consumption—I inspect mine every 30,000 kilometers for peace of mind and cost savings. After inspection, reinstall it according to the manual, ensuring it's tightened securely to keep the engine running smoothly.
