①Porcelain core is pale white

The porcelain core is pale, the center pole is melted or defective, the side pole tip is thinner and the surface is rough, and the surface of the shell extending into the cylinder has metal peeling and peeling, which indicates that the spark plug is overheated. It only appears on individual spark plugs in multi-cylinder gasoline engines, which may be caused by low calorific value (thermal type), misuse, poor quality, etc.; if the porcelain core is often white in a certain cylinder, the compression ratio of this cylinder should be checked Whether it is too high, or check whether the water jacket around the spark plug is blocked. For high compression ratios, attention should be paid to whether there is hot ignition; if the porcelain core is white in several cylinders at the same time, the reasons such as excessive load of the gasoline engine and insufficient cooling capacity should be considered, and a spark plug with a higher calorific value should be used.

②The porcelain core is blackish

is slightly black and covered with a thin layer of carbon powder. There are carbon deposits on the ring surface of the shell and even on the side electrodes. If this phenomenon occurs after a long period of cold and low-speed operation, it will be eliminated after a period of normal use. If the working conditions are too high in normal use, a low-calorific value spark plug should be used instead. After switching, pay attention to whether the spark plug is overheated, the center pole burns, or the cylinder is pulled when the gasoline engine is at high speed and high load.

③The porcelain core is brown and black

The color of the spark plug is brown and black, and the outer shell and side poles have thick hard lump carbon deposits. This is the performance of gasoline engine burning oil, and the oil enters from the piston ring or intake valve duct. Sometimes it is not the burning of the engine oil but the spark plug itself. It is obvious that the porcelain body is broken or the side electrode is broken. There are also unobvious reasons, and it should be checked for sparkover.