The nozzle (Figure 1) is designed to inject fuel into the diesel cylinder and provide high-quality fuel spray

Diesel engines use CRIN2 type injectors manufactured by BOSCH (Germany).


Picture 1 - Nozzle

The required start of injection and the amount of fuel supply are provided by the action of the injector solenoid valve.

The injection start time is set by the diesel electronic control system.

The formation of injector control signals by the electronic unit occurs on the basis of “reading” the signals generated by the crankshaft speed sensors and the input shaft of the injection pump drive gearbox, installed in a certain angular position one relative to the other.

The principle of operation of the nozzle is shown in Figure 2.

Fuel is supplied through the high-pressure line through the inlet channel 4 to the injector nozzle 11, as well as through the fuel supply throttle hole 7 - into the control piston chamber 8 through the fuel outlet throttle hole, which can be opened by a solenoid valve, the chamber is connected to the backflow line 1.

When the throttle hole 6 is closed, the hydraulic force acting from above on the control piston exceeds the force of fuel pressure from below on the chamfer (shoulder) 12 of the nozzle sprayer needle.

As a result, the needle is pressed against the atomizer seat and tightly closes the atomizer holes. As a result, fuel does not enter the combustion chamber.

When the solenoid valve 3 is activated, the armature of the electromagnet moves up and the ball 5 opens, opening the throttle hole 6.

Accordingly, both the pressure in the control valve chamber and the hydraulic force acting on the control valve piston are reduced.

Under the action of fuel pressure on the cone, the atomizer needle moves away from the seat, so that fuel enters the combustion chamber of the cylinder through the atomizer holes.

Control flow is the additional amount of fuel intended to lift the needle, which, after use, is diverted into the fuel return line.

Principal scheme of injector operation

Picture 2 - Schematic diagram of the injector operation

In addition to the control flow, there are fuel leaks through the atomizer needle and control piston guide.

All this fuel is discharged into the backflow line, to which all other units of the injection system are connected, and returned to the fuel tank.

The amount of fuel injected is proportional to the time the solenoid valve is turned on and the pressure in the rail, and does not depend on either the engine speed or the operating mode of the injection pump (time-controlled injection).

When the solenoid valve is de-energized, the armature is pressed down by the force of the valve locking spring and valve ball 5 closes the throttle port.

After closing the fuel outlet throttle, the pressure in the control valve chamber again reaches the same value as in the accumulator.

This increased pressure pushes down the control piston along with the atomizer needle. When the needle is firmly attached to the atomizer seat and closes its holes, injection stops.

Injector marking location

Replacement of injectors according to the results of testing the “COMMON RAIL” power supply system should be carried out taking into account the markings of the injector and sprayer, applied in the places indicated in Figure 3.

Replacing the atomizer in the nozzle without the use of special equipment and specially trained personnel, as well as during the warranty period, is prohibited.

During the warranty period, the atomizer in the nozzle can only be replaced by a Bosch service or workshops specially authorized by Bosch.