INTRODUCTION - INJECTORS AND PIPES

1.9 Multijet

INJECTORS

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 Classification

During 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 rod

2. Pin

3. Nozzle

4. Coil

5. Pilot valve

6.Spherical shutter

7. Control area

8.Supply volume

9. Control volume

10. Fuel return - low pressure

11. Control duct

12. Feed duct

13. Electrical connection

14. Fuel return connector - high pressure

15. Spring

16. IMA code

1.3 Multijet

INJECTORS

The injectors are fitted on the cylinder head and controlled by the injection control unit.

The injector may be divided into two sections:

- actuator/atomizer 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 line pressure acting on the control area (7) of the rod (1); Fa: due to 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 Classification

During the test stage the injectors are checked by controlling the specifications in various pressure/flow rate conditions. All the injectors that do not meet a certain standard are rejected; the remaining ones are graded with a nine digit alphanumerical code known as an IMA code, applied by laser to the top 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 rod

2. Pin

3. Nozzle

4. Coil

5. Pilot valve

6. Ball plunger

7. Control area

8. Feed volume

9. Control volume

10. Fuel return - low pressure

11. Control duct

12. Feed duct

13. Electrical connection

14. Fuel return connector - high pressure

15. Spring

16. IMA code

SINGLE FUEL MANIFOLD PIPE

The single fuel manifold (rail) is fited to the intake side of the cylinder head.

With a volume of around 20.5 cc, this dampens fuel pressure fluctuations due to:

- pressure pump operation

- injector opening.

There is a fuel pressure sensor (3) fitted on one side of the supply manifold (1) and the pressure regulator (2) is connected to the other side.

The hydraulic connections (high pressure) between manifold-pump and manifold-injecors are via steel pipes with a bore of 2 mm and external diameter of 6 mm.