At present, the fuel injection nozzle used in automobiles is actually a simple solenoid valve. When the solenoid coil is energized, the suction force will be generated, and the needle valve will be sucked up to open the injection hole. The fuel will be ejected at a high speed through the annular gap between the shaft needle and the injection hole at the head of the needle valve, forming a mist, which is conducive to full combustion. In the past, the fuel injection nozzle used in diesel engine was mechanically controlled, and the mechanical diesel nozzle worked by controlling the precision coupling parts (needle valve, needle valve body). The coupling parts of the nozzle is one of the three precision coupling parts of the traditional diesel engine, including plunger, plunger sleeve, needle valve, needle valve body, oil outlet valve and oil outlet valve seat. The nozzle of gasoline engine is a part of electronic control system of gasoline engine, which replaces the carburetor of carburetor type gasoline engine. The main nozzles used in automobiles include diesel nozzle, gasoline nozzle, natural gas nozzle, etc. now some foreign manufacturers can manufacture special nozzle for hydrogen.
The main causes of fuel injection nozzle sticking are as follows:
1. The diesel oil is not clean and there are impurities in the high-pressure oil pipe, so that the needle valve coupling parts are not closed tightly, and the high-pressure gas in the combustion chamber reverses and burns the needle valve coupling parts. In addition, the dirt on the pressure regulating spring and tappet of the injector moves to the upper part of the needle valve of the injector through the injector tappet, or the cotton rope and lead wire used to prevent oil leakage from entering the injector through the high-pressure oil pipe will cause the needle valve coupling to be stuck.
2. The engine temperature is too high and the fuel injector is not cooled well, which causes the delivery valve coupling to be stuck. However, too late fuel supply time, excessive scale or blockage of cooling water channel, wear of pump impeller end face and long-term overload of engine will make the engine overheat.
3. The wear of the delivery valve makes the fuel drop when the fuel injector stops fuel injection, which causes the fuel injector to burn coke and deposit carbon, resulting in stuck failure.
4. When the fuel injector is installed, the missing gasket or the gasket is damaged, resulting in air leakage, causing the local temperature of the injector to be too high and stuck.
5. The injection pressure is too low, which results in high pressure gas reverse channeling in combustion chamber;
6. The reasons for parts manufacturing are as follows: the injector mounting hole on the cylinder head matches the injector too tightly, the clearance between the needle valve body and the cylinder head is too small, and the machining of the injector mounting hole in the cylinder head is too deep.