Every year, the requirements for a diesel engine according to criteria such as power, environmental friendliness and efficiency only increase. And only an ideal formation of a combustible mixture can satisfy these requirements. Therefore, the entire injection system must work efficiently, providing the finest atomization under high pressure.
Such a system, which combines a fuel injector and a pump in one assembly, is a pump injector. Similarly to high pressure fuel pump, the pump nozzle injects a certain volume of the mixture at the right time. Due to the fact that each of the engine cylinders has one pump nozzle, in such a system there are no fuel injection pumps.
The nozzle device is as follows: diesel pump nozzles are located in the
cylinder head . To bring them into action on the camshaft there are 4 special cams. The force on the
plungers of the pump nozzles is transmitted through the rocker arms. Thanks to the special cam profile of the pump-injector drive, the beam first rises sharply and then gradually lowers.
At the moment when there is a sharp rise in the rocker arm, the plunger with great speed is pressed down. Therefore, high pressure arises. When the beam begins to lower slowly, the plunger also begins to
move slowly and
evenly . This design allows the fuel to flow smoothly into the high-pressure chamber without the formation of air bubbles. The time and period of the injection are controlled by the solenoid valve for controlling the pump nozzle. To do this, voltage is supplied to it through the electronic
control unit . Even with small deviations in the factory parameters, fuel is overspray when spraying, the engine begins to "make noise."
The diesel pump nozzle can be of three types: piezoelectric, electromagnetic, electro-hydraulic. With an electromagnetic valve, the nozzle is installed on both gasoline and diesel engines and has a simple device: a nozzle and an electromagnetic valve with a spraying needle. The electro-hydraulic nozzle is installed only on diesels, which most often work on the Komon Rail system. Piezoelectric is considered the most advanced for diesel engines.
Such a nozzle pump operates up to 4 times faster than an electromagnetic one, and doses the injected fuel with maximum accuracy.
Injector repair should be done when the following symptoms are observed: fuel consumption is noticeably increased, failure when the gas pedal is pressed quickly, fuel leaking or popping in the exhaust system. Idle turns of the car are unstable: the tachometer needle constantly "jumps" for no reason. The nozzles are checked, as well as their repairs are made on special stands, therefore it is difficult to repair them on their own: setting the pressure only 10% above the nominal value is the cause of engine malfunctions. And even if the operation of the fuel system does not give cause for concern, the diagnosis of injectors is a process that is recommended to be carried out after every 60,000-70,000 km of car mileage.