The injectors are fitted on the cylinder head and controlled by the injection control unit.The injector may be divided into two sections:- actuator/nebuliser consisting of pressure rod (1), pin (2) and nozzle (3);- control solenoid consisting of coil (4) and pilot valve (5).Injector operation is divided into three stages.REST POSTION, the coil (4) is deactivated and the shutter (6) is in the closed position to prevent fuel from being introduced into the cylinder Fc > Fa (Fc: due to the line pressure acting on the control area (7) of the rod (1); Fa: due to the line pressure acting on the feed volume (8).START OF INJECTION, the coil (4) is energized and causes the shutter (6) to rise.Control volume fuel (9) flows out towards return manifold (10) to bring about a pressure drop on control area (7). Simultaneously, the line pressure flowing through the intake duct (12) exercises a force Fa > Fc in the supply volume (8) to cause the pin (2) to lift and allow fuel into the cylinders.END OF INJECTION, the coil (4) is deactivated and causes the shutter (6) to return to closed position. This rebalances the forces so that the pin (2) returns to the closed position and the injection ends.IMA ClassificationDuring the test stage the injectors are checked with the specifications verified in different pressure/flow rate conditions. All the injectors that do not meet a certain standard are rejected; the remaining ones are classified using a 9 character alphanumerical code, known as an IMA code, imprinted by laser on the top part of the magnet.During fitting on the vehicle the control unit should memorize the individual code and, if one or more injectors is replaced in a service situation the alteration to the code should be made during the diagnosis using the appropriate equipment.
1. Pressure rod2. Pin3. Nozzle4. Coil5. Pilot valve6.Spherical shutter7. Control area8.Supply volume9. Control volume10. Fuel return - low pressure11. Control duct12. Feed duct13. Electrical connection14. Fuel return connector - high pressure15. Spring16. IMA code
