Injection pump: classification and repair

Every year, the requirements for a diesel engine on criteria such as power, environmental friendliness and economy only increase. And only an ideal formation of a combustible mixture allows satisfying these requirements. Consequently, the entire injection system must work efficiently, providing the smallest spray at high pressure.

Such a system, which combines a fuel injector and a pump in one unit, is a pump-injector. Similarly to injection pumps, the injector pump injects a specific volume of the mixture at the right time. Due to the fact that for each of the engine cylinders there is one pump-injector, in such a system there are no fuel pipes of fuel pump.

The nozzle arrangement is as follows: diesel injectors are located in the cylinder head . To actuate them on the camshaft there are 4 special cams. The force on the plungers of the injector pumps is transmitted through the rocker arms. Due to the special profile of the drive cam of the pump-injector, the rocker first rises sharply and then smoothly descends.

At the moment when the rocker rises sharply, the plunger presses down at a tremendous speed. Therefore, a high pressure arises. When the rocker starts to slowly lower, the plunger also starts to move slowly and evenly upwards. This design allows the fuel to flow into the high pressure chamber smoothly, without creating air bubbles. The time and the injection period control the solenoid valve control pump-injector. To do this, the electronic control unit is supplied with voltage. Even with small deviations in the factory parameters, during spraying the fuel is over-consumed, the engine starts to "make noise".

Diesel pump-injector can be of three types: piezoelectric, electromagnetic, electro-hydraulic. With the solenoid valve, the nozzle is installed on both petrol and diesel engines and has a simple device: a nozzle and a solenoid valve with a spray needle. Electro-hydraulic injector is installed only on diesel engines, which most often work on the system of Komon Rile. Piezoelectric is considered the most perfect for diesel engines. This injector pump operates up to 4 times faster than the electromagnetic injector, and doses the injected fuel with maximum accuracy.

Repair of injectors should be made when the following signs are observed: fuel consumption is significantly increased, a failure with a rapid depression of the gas pedal, leakage of fuel or clap in the exhaust system. Idle turns of the car are unstable: the arrow of the tachometer constantly "jumps" for no reason. Checking the injectors, as well as their repair is done on special stands, therefore it is difficult to repair them yourself: setting the pressure only 10% higher than the nominal causes the engine to malfunction. And even if the operation of the fuel system does not give cause for concern, the diagnosis of the injectors is a process that is recommended to be carried out after every 60,000-70,000 km of auto run.