ELECTRIC/ELECTRONIC COMPONENTS 766161 Electronic control unit MS6.3 or

At the same time, line pressure through feed duct (12) applies a force Fa > Fc in pressure chamber (8) lifting peg (2), with fuel being consequently introduced into cylinders.

- ”end of injection”

The coil (4) is de-energized and makes the shutter (6) return to its closed position. This recreates such a balance in the forces as to make the pin (2) return to its closed position and consequently end injection.

1 Pressure rod — 2 Pin — 3 Nozzle — 4 Coil — 5 Pilot valve — 6 Ball shutter — 7 Control area — 8. Pressure chamber —

9 Control volume — 10 Low-pressure fuel return — 11 Control pipe — 12 Supply pipe — 13 Electrical connection

— 14 High-pressure fuel inlet fitting — 15 Spring.

The electro-injector can be divided into two parts:

- actuator/jet composed of pressure rod (1), pin (2) and nozzle (3);

- control solenoid valve composed of coil (4) and pilot valve (5).

Operation

Electro-injector operation can be broken down into three phases:

- ”rest position”

Coil (4) is de-energised, and shutter (6) is in closing position and prevents fuel from being introduced into the cylinder, Fc

> Fa (Fc: caused by fuel pressure acting on control area (7) of rod (1); Fa: caused by line pressure acting on pressure chamber (8).

- ”start of injection”

50704

Figure 272

ELECTRIC/ELECTRONIC COMPONENTS 766161 Electronic control unit MS6.3 or

EDC 16

The control unit is a ”flash EPROM” and so it can be reprogrammed from outside without changing the hardware.

It processes the signals from the sensors by applying software algorithms and controls the actuators (especially the electro-injectors and pressure regulator).

The injection control unit has the absolute pressure sensor built in to further improve the control of the injection system.

The control unit is mounted on the left-hand side of the engine bay and is connected to the vehicle’s wiring harness by two 43-pin connectors:

MS6.3:

— 43-pin connector A for the components on the engine

— 43-pin connector B for the components on the vehicle EDC.16:

— 60-pin connector A for the components on the engine

— 94-pin connector K for the components on the vehicle In addition to handling the operation of the system described under the relevant heading, the electronic control unit is interfaced with the other electronic systems on the vehicles such as ABS — EBD cruise control, speed limiting device, immobilizer (IVECO CODE), EGR and glow plugs.

90638

Fc

Fa

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Print 603.43.351

SENSORS

Engine speed sensor

It is an inductive type sensor and is positioned on the phonic wheel mounted on engine shaft front end.

It generates signals obtained from magnetic flux lines which close through phonic wheel teeth. Teeth number: 58.

The electronic control unit uses this signal to measure the speed of rotation of the engine, its angular position and to operate the electronic rev counter.

If this signal fails the rev counter will not work.

Camshaft timing sensor

It is a Hall effect type sensor positioned on camshaft pulley.

It generates signals obtained from lines of magnetic flux that close through a notch in the pulley.

The signal generated by this sensor is used by the electronic control unit as a redundant signal to measure the different en-gine speeds.

772655 Air temperature and pressure sensor Positioned on the intake manifold, it measures the pressure of the turbocharging air introduced into the intake manifold.

This value, together with that of the air temperature sensor, makes it possible for the electronic control unit to calculate the exact quantity of air introduced into the cylinders so as to operate the injectors adjusting the fuel delivery, limiting harmful emissions, improving consumption and performance.

The sensor contains an electronic temperature correction circuit to optimize the pressure measurement in relation to the temperature of the intake air.

772656 Fuel temperature sensor

Integrated in the fuel filter, it measures the fuel temperature and transmits it to the electronic control unit.

When the fuel temperature is too high (ambient temperature condition, engine at full load and tank in reserve), correct lubrication of the high-pressure pump is no longer assured. On the basis of the values received, the control unit determines the density and volume of the fuel, correcting the delivery limiting engine performance.

774511 Fuel pressure sensor

This is mounted in the middle of the hydraulic accumulator (rail) and it has the task of providing feedback for the injection control unit to:

- adjust injection pressure - adjust the duration of injection.

766161 Atmospheric pressure sensor

This is integrated in the electronic control unit. It provides a criterion of correction for the measurement of the air flow rate and to calculate the reference air flow rate to check the EGR.

Figure 273

761917 Glow plug electronic control unit

The engine control unit, in the phase of:

- starting - after-starting

times the operation of the glow plug control unit according to the engine temperature.

Glow plugs drive is through glow plugs pre-heating central unit depending on engine temperature under close control of engine control central unit.

The pre-heating control unit contains an “intelligent”

contactor that sends feedback to the control unit that is thus informed about any fault with the pre-heating control unit or shorting to earth of the glow plugs.

75578

761915 Glow plugs Figure 274

75579

CONTROL VALUES

With a constant supply voltage of 11 V:

- max. current drawn 18 A

- in 5 sec. 11±1.5 A

- in 30 sec. 6±0.9 A

- temperature after 7 sec. 850°C

- tightening torque 8-10 Nm

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ACTUATORS

The injection system comprises three classes of actuators interlocked with the electronic control unit:

- electro-injectors (see relevant heading);

- regulators (see relevant headings) requiring PWM control (Pulse Width Modulation):

• for pressure

• EGR (if mounted)

• turbocharger with variable geometry (if mounted);

- actuators with continuous ON/OFF signal to:

• engage electromagnetic coupling for radiator cooling fan;

• turn on/off air-conditioner compressor (if mounted);

• Cruise Control;

• starter heater control;

• fuel filter heating;

• electric supply pump.

PWM (Pulse Width Modulation) controls A PWM control has an active and an inactive state that alternate within a constant set length of time. During the active state the actuator control circuit is closed, which is thus powered with the control voltage; whereas, during the inactive state the circuit is open.

The duration of the two states may be varied with the condition that the sum of the two times is equal to the length of the modulation delivery.

The duration of the active state determines the duty-cycle, which is normally expressed as a percentage of the total time.

Therefore, if the duration of the two active and passive states are the same, the duty-cycle is equal to 50%.

For reasons of diagnostics, the duty-cycle is limited between 1% and 99%; the control resolution is equal to 0.005%

(1/20000 of the time).

The time length has been chosen taking account of the dynamic actuator response specifications.

Too low a carrier frequency could cause oscillations in the actuator, while too high a frequency would decrease control resolution.

The E.G.R. and variable geometry turbocharger (if mounted) are controlled through a vacuum modulating valve.

764254 Engine coolant temperature sensor This provides the control unit with an index of the thermal status of the engine in order to determine corrections for the fuel delivery, injection pressure, EGR injection advance when starting cold (if mounted) and warm-up.

505910 Throttle pedal position sensor The accelerator pedal position sensor provides the control unit with a voltage value in proportion to the angle of operation of the pedal determining fuel delivery.

772641 Clutch pedal position sensor

Mounted on the pedal board, it provides the control unit with a positive signal when the clutch is engaged (pedal released).

Every time the clutch is disengaged to change gear, the control unit fails to receive this signal and deactivates the Cruise Control function.

772642 Brake pedal position sensor

There are two of these sensors mounted on the pedal board.

With the brake pedal released, they provide the control unit with a positive signal that is used to detect brake operation so as to deactivate the Cruise Control function and stop delivery of fuel.

In addition, a sensor switches on the brake lights.

764261 Vehicle speed sensor

This sensor, mounted on the gearbox by the drive output shaft, transmits the vehicle speed signal, through the electronic tachograph, to the control unit.

All the power controls are made with relays located in the cab.

NOTE

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86435

1. 38-pole diagnostic socket.

Figure 275

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GUIDE TO TROUBLESHOOTING