The main reasons for stuck fuel injectors are

1. The diesel fuel is not clean, and there are impurities in the high-pressure fuel pipe, which causes the needle valve coupling to be not tightly closed. The high-pressure gas in the combustion chamber is backflowing, and the needle valve coupling is burned out. In addition, dirt on the pressure regulating spring, tappet and other parts of the fuel injector moves to the upper part of the fuel injector needle valve through the fuel injector tappet, or cotton ropes and lead wires used to prevent oil leakage on the oil circuit enter the fuel injector through the high-pressure oil pipe, which can cause the needle valve coupling to become stuck.
2. Excessive engine temperature, poor cooling of the fuel injector, resulting in stuck needle valve components. Delayed fuel supply, excessive or clogged cooling water channels, worn end faces of water pump impellers, and long-term overload of the engine can cause the engine to overheat.
3. The wear of the fuel outlet valve causes dripping of fuel when the fuel injector stops spraying, resulting in coking and carbon accumulation at the nozzle, leading to a malfunction of jamming.
4. During the installation of the fuel injector, missing or damaged gaskets can cause air leakage, causing the local temperature of the fuel injector to be too high and become stuck.
5. The injection pressure is too low, causing high-pressure gas in the combustion chamber to reverse flow;
6. Due to manufacturing reasons, such as tight fit between the fuel injector mounting hole on the cylinder head and the fuel injector, small gap between the needle valve body and the mounting hole on the cylinder head, and deep machining of the fuel injector mounting hole on the cylinder head.