Operation

IMPORTANT

Before any work on the injection system, use the diagnostic tool to check:

• that the rail is no longer pressurized,
• that the fuel temperature is not high.

Always observe the safety and cleanliness instructions given in this document during every operation.

Never loosen a high-pressure pipe connection while the engine is running.

The "common rail" high-pressure injection system operates in sequential mode (based on the operation of multipoint injection for petrol engines).

Thanks to pre-injection, this injection system:

• reduces operating noise,
• lowers the quantity of particulates and polluting gases,
• provides high engine torque from low engine speeds.

The high-pressure pump generates the high pressure and delivers it to the injection rail. The actuator on the high-pressure pump controls the quantity of diesel supplied according to the demand determined by the ECU. The rail supplies each injector through a steel pipe.

The ECU:

• determines the injection pressure value required for correct engine operation, then controls the flow actuator. It checks that the pressure value is correct by analysing the value sent by the pressure sensor on the rail,
• determines the injection time required to deliver the correct quantity of diesel at the moment injection must begin,
• electrically controls each injector individually after determining these two values.

The fuel flow injected into the engine is determined by:

• the injector drive duration,
• the opening and closing speed of the injector,
• the needle lift (determined by a constant for each injector type),
• the nominal hydraulic flow rate of the injector (unique to each injector),
• the high-pressure rail pressure regulated by the ECU.

K9K

The ECU manages:

• idle speed control,
• exhaust gas recirculation (EGR) flow to the intake,
• fuel supply control (timing, quantity and rail pressure),
• cooling fan control request (function: centralised coolant temperature management),
• air conditioning,
• cruise control / speed limiter function,
• glow plug pre- and post-heating control.

The high-pressure pump is supplied at low pressure by a mechanical transfer pump (feed pump).

The high-pressure pump supplies the rail, whose pressure is controlled:

• for charging, by the flow actuator,
• for discharge through the injector valves.

Pressure drops can thus be compensated.

The flow actuator allows the high-pressure pump to deliver only the quantity of diesel needed to maintain pressure in the rail. This component minimises heat generation and improves engine efficiency.

To relieve the rail, the injector valves are driven with short electrical pulses:

• short enough not to open the injector (flow through the injector return circuit),
• long enough to open the valves and relieve the rail.

Control of the cooling fan and the coolant temperature warning light on the instrument panel by the injection ECU (function: centralised coolant temperature management).

K9K

The vehicle's control units communicate via a multiplexed link. Therefore, the fault warning lights on the instrument panel are activated via the multiplex network.

In the event of a collision, the diesel supply cut-off function is managed by the airbag control unit.

It instructs the injection ECU, via the multiplex network, to lock the control of the injection lock relay.

Unlocking only becomes active after the ignition has been switched off for 10 seconds. This operation will cause the fault warning light to remain on longer than usual when the ignition is switched on. The light will only return to normal operation after the fault has been erased using the diagnostic tool.

Vehicle speed information is sent to the instrument panel via the multiplex network by the ABS control unit or the vehicle speed sensor box (vehicles without ABS).

Some vehicles have a water-in-diesel sensor located on the filter. If water is present in the diesel, the orange injection warning light comes on.

Automatic configuration for the operation of the cruise control / speed limiter and the air conditioning.

Injection ECU controlling the air conditioning compressor clutch via the protection and switching unit.

A new electronic module called the "protection and switching unit" is added to the vehicle's electrical circuit.

The protection and switching unit supplies power to:

• the air conditioning compressor,
• the cooling fan assembly,
• the electric heater resistors.

The protection and switching unit is located in the engine compartment near the battery.

It helps protect certain electrical components.

For this function, it includes:

• fuses,
• several internal relays, including:

• the "+ after ignition" relay,
• the cooling fan control relays,
• the air conditioning compressor control relay.

These relays cannot be disassembled.

Replacing a protection and switching unit requires configuring it with the diagnostic tool (see chapter Engine interconnection box).

The injection ECU continuously receives, via the multiplex network, information on the electrical power available from the alternator. This prevents the vehicle's electrical consumption from exceeding the alternator's capacity. The priority is to recharge the battery.

WARNING

• The engine must not run on diesel containing more than 10% biodiesel (FAME), or even a very small quantity of petrol.
• Do not disassemble the inside of the high-pressure pump or the injectors. Only the flow actuator, the diesel temperature sensor and the venturi may be replaced.
• Do not remove the rail pressure sensor from the injection rail, to avoid contaminating the circuit. If the pressure sensor fails, replace the assembly consisting of the pressure sensor, the rail and the five high-pressure pipes.
• Never remove any injection pump pulley bearing number 070 575.

  When replacing the pump, replace the pulley.

• Do not supply any system component directly with +12 V.
• Decarbonising and ultrasonic cleaning are prohibited.
• Never start the engine unless the battery is properly connected.
• Never turn the engine against its normal direction of rotation.

F9Q

Bleed the circuit using the priming pump.

IMPORTANT

The engine must not run on diesel containing more than 10% biodiesel.

Note: After any work, check for diesel leaks. Run the engine at idle until the cooling fan starts, then perform several no-load accelerations.

The system can inject diesel into the engine at pressures up to 1350 bar. Before each operation, check that the injection rail is no longer under pressure.

The tightening torque must be strictly observed for:

• high-pressure pipes,
• injector to cylinder head,
• pressure sensor and pressure regulator.

When repairing or removing the high-pressure pump, injectors, or supply, return and high-pressure outlet fittings, the ports must be fitted with new, suitable plugs to prevent contamination.

WARNING Any pipe removed must be replaced.

When replacing a high-pressure pipe, follow this procedure:

• remove the high-pressure pipe, holding the filter stem on the injector with a counter-wrench,
• fit the cleanliness plugs,
• loosen the high-pressure rail,
• fit the new high-pressure pipe,
• hand-tighten the fittings until they make contact,
• Tighten the high-pressure rail mounting bolts to torque.
• Tighten the injector-side connector to torque.
• Tighten the high-pressure rail-side connector to torque.

WARNING

Do not disassemble the internal parts of the pump.

The fuel return hose fitted to the injectors must be replaced whenever it is removed.

The diesel temperature sensor cannot be disassembled. It is part of the fuel return rail.

Do not loosen a high-pressure pipe connection while the engine is running.