System operation

The high-pressure injection system is designed to deliver a precise quantity of diesel to the engine at a specific moment.

It is fitted with a 112-pin BOSCH ECU of type "EDC16".

The system consists of:

• a priming pump on the low-pressure circuit,
• a diesel fuel filter,
• a high-pressure pump incorporating a feed pump (transfer pump),
• a high-pressure regulator fitted to the pump,
• an injection rail,
• a diesel pressure sensor integral with the rail,
• four solenoid injectors,
• a diesel temperature sensor,
• a coolant temperature sensor,
• an upstream intake air temperature sensor,
• a cylinder reference sensor,
• an engine speed sensor,
• a boost pressure sensor,
• an accelerometer,
• an exhaust gas recirculation solenoid valve,
• an accelerator pedal potentiometer,
• an atmospheric pressure sensor integrated into the injection ECU,
• the injection ECU,
• an air mass meter,
• a boost limiting solenoid valve,
• a throttle flap solenoid valve.

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

Thanks to the pilot injection process, this injection system reduces operating noise, lowers particulate and polluting gas emissions, and delivers high engine torque from low engine speeds.

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

a) The ECU:

It determines the injection pressure value required for correct engine operation, then controls the pressure regulator. It checks that the pressure value is correct by analysing the value sent by the pressure sensor on the rail.

It determines the injection time needed to deliver the correct quantity of diesel and the moment at which injection must start.

It 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 rail pressure (regulated by the ECU),
• 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 ECU manages:

• idle speed control,
• exhaust gas recirculation (EGR) flow to the intake,
• fuel supply control (timing, quantity and rail pressure),
• control of the cooling fan unit via the Protection and Switching Unit (G.C.T.E. function: Centralised Coolant Temperature Management),
• air conditioning (cold loop function),
• cruise control / speed limiter function,
• control of the pre/post-glow system,
• control of the warning lamps via the multiplexed network.

The high-pressure pump is supplied at low pressure by an integrated booster pump (transfer pump).

It supplies the rail, whose pressure is controlled for charging by the flow actuator and for discharging by the injector valves. Pressure drops can thus be compensated. The flow actuator allows the high-pressure pump to supply only the quantity of diesel needed to maintain pressure in the rail.

Thanks to this component, heat generation is minimised and engine efficiency is improved.

To relieve the rail through the injector valves, the valves are actuated with short electrical pulses: small enough not to open the injector (flow through the return circuit from the injectors), long enough to open the valves and relieve the rail.

• Multiplexed link between the vehicle's different control modules.

As a result, the fault warning lamps on the instrument panel are lit via the multiplexed network.

The instrument panel vehicle speed signal is sent by the anti-lock braking system module or the WHEEL SPEED Central Electronic Unit via a wired link, then broadcast over the multiplexed network by the instrument panel. The main users of the vehicle speed signal are the injection ECU and the airbag ECU.

Some vehicles use a water-in-diesel detection sensor, located in the filter. If water is present in the diesel, the injection and pre/post-heating warning light (orange) comes on.

IMPORTANT

The engine must not be run with:

• diesel containing more than 10 % diester,
• even small quantities of petrol.

The system can inject diesel into the engine at pressures of up to 1350 bar. Before each job, check that the injection rail is no longer pressurised and that the fuel temperature is not too high.

During every job on the high-pressure injection system, observe the cleanliness and safety rules set out in this document.

Do not disassemble the inside of the pump or the injectors. Only the flow actuator, the diesel temperature sensor and the venturi may be replaced.

For safety reasons, it is strictly forbidden to loosen a high-pressure pipe connection while the engine is running.

Due to fuel circuit contamination risks, do not remove the fuel rail pressure sensor from the fuel rail. If the pressure sensor is faulty, replace the pressure sensor, the fuel rail and all five high-pressure pipes.

It is strictly forbidden to remove any injection pump pulley marked 070 575. If the pump is replaced, the pulley must be replaced as well.

Do not supply any system component directly with +12 V.

Decarbonising and ultrasonic cleaning are forbidden.

Never start the engine unless the battery is reconnected correctly.

Disconnect the injection ECU before carrying out any welding on the vehicle.

b) Hosted functions

• Air conditioning management assistance

On air-conditioned models, the EDC16 system can switch off the air conditioning via the Cabin Central Unit under certain operating conditions:

• Voluntary interruption by the driver,
• During engine starting phases,
• In case of overheating (to reduce the power demanded from the engine),
• When engine speed is held at a very high level (compressor protection),
• During transient phases (such as strong acceleration demands for overtaking, kickdown and take-off). These conditions are only taken into account when they do not occur repeatedly, in order to avoid system instability (untimely deactivations).
• When certain faults are cleared.

• Air conditioning management in cooling loop

The air conditioning is of the cold loop type; its control is shared between several ECUs. The injection ECU is responsible for:

• Permit the cooling request based on: refrigerant pressure, coolant temperature, engine speed.
• Calculate the power absorbed by the compressor (from the refrigerant pressure).
• Request cooling fan unit control from the Protection and Switching Unit based on vehicle speed, refrigerant pressure and engine coolant temperature.

To reduce heating time, resistive air heating elements called positive temperature coefficient (PTC) resistors are included in the cabin heating circuit. The Cabin Central Unit determines whether the PTC resistors must be activated, the Protection and Switching Unit physically controls the PTC resistors, and the injection ECU determines, on the one hand, the power control limit of the PTC resistors based on alternator load and, on the other hand, the PTC resistor inhibition based on engine speed, load and vehicle speed.

• Speed limiter - cruise control management

When activated, the cruise control function maintains the vehicle speed at a preselected value, whatever the driving conditions encountered. The driver can increase or decrease the vehicle speed using the control buttons.

The cruise control function can be deselected either by the control buttons, by deactivating the cruise control function selector switch, or by the detection of system events such as brake or clutch pedal application, or by the detection of system faults such as inconsistent vehicle speed or excessive vehicle deceleration.

The regulation function can also be temporarily inhibited when the driver, by pressing the accelerator pedal beyond the regulation flow rate, wishes to take back control of the vehicle and exceed the selected set speed. Speed regulation resumes when the driver releases the accelerator pedal.

It is possible to reactivate the vehicle speed control and resume the last set speed following deactivation of the function for any reason during the same vehicle operating cycle (ECU power not switched off). The vehicle will then attempt to reach the set speed using a controlled speed ramp.

When activated (using the selector switch), the speed limiter function limits the vehicle speed to a preselected value. The driver controls the vehicle normally using the accelerator pedal up to the set speed. If the driver tries to exceed this speed, the system ignores the pedal demand and controls the vehicle speed as the cruise control would, provided the accelerator pedal is kept sufficiently depressed.

As with cruise control, the set speed can be changed using the control buttons, either by a momentary press or by a continuous press.

For safety reasons, the set speed can be exceeded by pressing the accelerator pedal beyond a pedal position limit value. Control is then entirely by the accelerator pedal until the vehicle speed drops below the set speed, at which point the limiter becomes active again.

The driver has the following controls for the cruise control / speed limiter function:

• accelerator pedal,
• brake pedal,
• clutch pedal,
• function selector switch used to choose cruise control or speed limiter operating mode,
• steering wheel controls.

c) Warning light management

• Instrument panel display

The ECU manages the instrument panel display of certain information relating to engine operation.

This covers five functions: the "OBD" (On Board Diagnostic) emissions warning light, glow plug pre/post-heating, coolant temperature, and engine faults: Severity 1 (non-critical fault) and Severity 2 (emergency stop). These five functions are represented by 3 indicator lights or messages displayed by the on-board computer.

• Glow plug pre-heating warning light

This lamp is used both as an operating indicator and as a system fault indicator:

• Steady illumination at + after ignition on: indicates glow plug pre-heating.
• Steady illumination with the message "Injection fault": indicates a Severity 1 fault (implies reduced operation and limited safety level. The user must carry out repairs as soon as possible).

• Temperature warning light - emergency stop

This warning light is used both as an operating indicator and a system fault indicator. It lights for 3 seconds at power-up (automatic test procedure managed by the instrument panel).

• Steady illumination: indicates engine overheating.
• Steady illumination with the message "Engine stop": indicates a Severity 2 fault.

In the case of a Severity 2 fault, injection is automatically cut off after a few seconds.

In the case of overheating, the driver remains free to stop the vehicle or not.

• "O.B.D." (On Board Diagnostic) emissions warning light

Symbolised by an engine, it lights when the ignition is switched on for about 3 seconds. It must never be illuminated with the engine running.

INJECTOR DIAGNOSIS

A) Check the resistance between pins 1 and 2 of each injector: 0.33 Ω at 20 °C. Check the insulation, continuity and absence of parasitic resistance of the following connections:

Engine ECU, grey connector C pin H1 → Pin 1 of injector No. 1 connector
Engine ECU, grey connector C pin G3 → Pin 2 of injector No. 1 connector
Engine ECU, grey connector C pin G2 → Pin 1 of injector No. 2 connector
Engine ECU, grey connector C pin G4 → Pin 2 of injector No. 2 connector
Engine ECU, grey connector C pin H2 → Pin 1 of injector No. 3 connector
Engine ECU, grey connector C pin H4 → Pin 2 of injector No. 3 connector
Engine ECU, grey connector C pin G1 → Pin 1 of injector No. 4 connector
Engine ECU, grey connector C pin H3 → Pin 2 of injector No. 4 connector

Carefully check the clips and latches of each injector connector.

If the vehicle starts:

• With the engine running, disconnect the injectors one after another (one at a time only).
• Replace the injector whose disconnection causes no change in engine operation.
• Clear the faults caused by the multiple disconnections, then carry out a road test.

B) Check the balance of injector return flows. Fit tappings on the injector returns to measuring vessels, start the engine and check the balance of the return flows at idle.

(In general, return flows are small. They must not come out as a "jet".)

• Replace the injector whose return flow is very different from the other injectors.

If there is low pressure in the rail:

• Replace the injector whose return shows a leak that is much greater than the others.

If the engine does not start: it is possible to check the return flows during and after a starting attempt (minimum 250 rpm) with the pressure regulator disconnected.

This causes high pressure in the rail and allows the return flows to be analysed. After the operation, clear the fault caused by disconnecting the pressure regulator.

C) Check the injector nozzle sealing.

• Check the engine oil level and condition:
• If there is diesel contamination, the nozzle of the leaking injector will be covered in soot and the cylinder will be "fuel-fouled".

Make sure these traces are not caused by engine oil being drawn up into the cylinder, by checking the engine compressions.

If the compressions are within specification, locate the faulty injector by inspecting the condition of the cylinders and pistons through the glow plug holes (fuel-fouled cylinder, overheating and start of piston damage). If the cylinder and piston inspection is inconclusive, remove the injectors and replace the one whose nozzle is covered in soot.

Note: After replacing an injector, follow the injector code programming procedure (see the "Component replacement" section).

WARNING

For injector removal and refitting, observe the cleanliness and safety instructions given in the "General" section.