On the one hand, the oil inlet screen of the nozzle is blocked by tiny substances deposited in gasoline for a long time. When the car is cold, the gasoline has high viscosity and poor fluidity, which leads to the gasoline not passing through the nozzle smoothly, resulting in insufficient gasoline injection. On the other hand, the needle valve is stuck due to carbon deposition on the head of the injector. When the fuel injector coil is energized, the needle valve can't be opened or the opening stroke of the needle valve is not enough, and the nozzle area of the fuel injector becomes smaller, resulting in smaller fuel injection or poor atomization. Nozzle failures are mostly reflected in cold cars, especially in winter. The lower the engine temperature when the cold car starts, the greater the increase of gasoline injection. This is mainly because when the engine starts at low temperature, the gasoline in the intake valve and the inner wall of the cylinder vaporizes poorly, and some gasoline can't be fully volatilized and burned, resulting in too thin mixture in the cylinder, which makes the engine difficult to start cold, unstable idle speed and flameout, and the fault phenomenon disappears after the engine warms up. According to the correct maintenance cycle and the standard, the daily maintenance of the engine fuel system can avoid the blockage of the fuel nozzle.