Scarring, damage to the tip of the spark plug, or melting or ablation of the electrode indicates that the spark plug has been damaged and should be replaced. Check for signs of ablation and color changes during replacement to analyze the cause of the failure.

① The electrode is melted and the insulator is white. It indicates that the temperature in the combustion chamber is too high. This may be due to excessive carbon deposits in the combustion chamber, excessively small valve clearances, etc., which may cause the exhaust valve to overheat or the cooling device to work poorly.

② The electrode is rounded and the insulator is scarred. It indicates that the engine is prematurely burned, which may be due to premature ignition time, low gasoline octane number, high spark plug heat value, etc.

③ The top of the insulator is broken. Knocking combustion is the main cause of insulator rupture. Too early ignition time, low gasoline octane number, and too high temperature in the combustion chamber may cause engine knocking combustion.

④ There are gray-black stripes on the top of the insulator. This stripe indicates that the spark plug has leaked and should be replaced with a new one.

Spark plug has deposits

There is sometimes deposits on the tip of the spark plug insulator and between the electrodes, which can cause the engine to stop working in severe cases, such as cleaning the spark plug can be temporarily remedied. To maintain good performance, the root cause of the failure must be identified.

① Oily sediment. Oily deposits on the spark plugs indicate that lubricant has entered the combustion chamber. If it is only an individual spark plug, the valve stem oil seal may be damaged. If such deposits are stuck to the spark plugs of each cylinder, it indicates that the cylinders are leaking oil, and the air filters and ventilation devices should be checked for blockages.

② Black sediment. There are black deposits inside the spark plug electrode and inside, indicating that the mixed gas is too rich, which can increase the engine's running speed, and last for a few minutes, you can burn off a layer of black soot left on the electrode.