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INTRODUCTION - DIESEL FUEL INJECTION SYSTEM

CHARACTERISTICS

FUNCTION

The EDC-17C49 Common Rail system is a high pressure electronic injection circuit for fast, direct injection diesel engines.

Its main features are:

  • availability of high injection pressure (up to 1600 bar);

  • possibility of modulating these pressures between 150 bar up to the maximum operating pressure of 1600 bar, independently of the

  • rotation speed and engine load;

  • ability to work at high engine rpms (up to 5000 rpm in full load conditions);

  • precision injection control (injection advance and duration);

  • reduced fuel consumption;

  • reduced emissions.

The main functions of the system are basically as follows:

  • fuel temperature control;

    engine coolant temperature control;

    control of amount of fuel injected;

    idle speed control;

    fuel cut-off during over-run;

    cylinder balance control from idle speed up to 3500 rpm;

    control of anti-judder function;

    control of exhaust fumes during acceleration;

    exhaust gas recirculation control (E.G.R.);

    maximum torque limit control;

    maximum speed limit control;

    heater plug control;

    control of climate control system activation (where fitted);

    auxiliary fuel pump control;

    cylinder position control;

    main and multiple injection advance control;

    closed cycle injection pressure control;

    electrical balance control;

    IMA injector calibration.

INJECTION DIAGRAM


1. Fuel tank

2. Fuel electric pump

3. Fuel filter

4. Fuel return manifold

5. High pressure pump

6. Fuel pressure regulator

7. Single fuel manifold (rail)

8. Fuel pressure sensor

9. Injectors

10. Air cleaner

11. Flow meter

12. Air compressor

13. Intercooler

14. Throttle body

15. EGR valve

16. EGR heat exchanger

17. Exhaust gas supply pipe to intake chamber

18. Air pressure - temperature sensor

19. Engine rpm sensor

20. timing sensor

21. Coolant temperature sensor

22. Engine oil pressure sensor

23. Engine oil level sensor

24. Heater plugs

25. Heater plug control unit

26. Turbine

27. Pneumatic actuator for turbocharger wastegate valve

28. Turbocharger wastegate valve pneumatic actuator control solenoid valve

30. Oxygen sensor

31. Catalytic converter

32. Particle filter (DPF)

33. Exhaust gas temperature sensor

34. Particulate filter differential pressure sensor

35. Accelerator pedal potentiometer

36. Engine management control unit

37. Exhaust gas cooling by-pass for E.G.R.

38. Exhaust gas cooling by-pass control for pneumatic actuator E.G.R.

OPERATION

Operating strategies

General information

The Common Rail system makes it possible to carry out a pre-injection (pilot injection) before T.D.C. This has the advantage of reducing the pressure shift in the combustion chamber, thus reducing the combustion noise typical of direct injection engines.

The control unit controls the quantity of fuel injected, regulating the line pressure and injection times.

The control unit processes the following information in order to control the quantity of fuel to inject:

  • engine rpm;

  • coolant temperature;

  • turbocharging pressure;

  • air temperature;

  • aspirated air quantity;

  • battery voltage;

  • diesel pressure;

  • accelerator pedal position.

Diagram of information entering/leaving the control unit


1, Auxiliary fuel pump

2, Turbocharging pressure control solenoid

3, Air conditioner compressor

4, E.G.R. solenoid

5, Rev counter (via CAN)

6, Electric fans

7, Heater plugs control unit

8, Accelerator pedal potentiometer

9, Brake - clutch pedal switch

10, Fuel pressure sensor

11, Air flow meter

12, Coolant temperature sensor

13, Fuel temperature sensor

14, Cruise Control (where fitted) (via CAN)

15, Air pressure and temperature sensor

16, Timing sensor

17, Rpm sensor

18, Speedometer (via CAN)

19, Battery

20, FIAT CODE (via CAN)

21, Diagnostic socket (via CAN)

22, Pressure regulator

23, Injectors

24, Heater plugs

25, Throttle solenoid (on throttle body)

26, Heater plugs warning light (via CAN)

27, Injection warning light (via CAN)

28, Water max temperature warning light (via CAN)

29, Water in fuel warning light (via CAN)

Self-diagnosis

The control unit self-diagnosis system checks the signals coming from the sensors and compares them with the permitted limits.

FAULT SIGNALS DISPLAYED DURING START UP:

  • warning light stays on for 4 seconds to indicate test stage;

  • the warning light goes out after 4 seconds to indicate there are no faults in components that could alter the values imposed by pollution control regulations;

  • if the warning light is still on after 4 seconds, this indicates a fault.

FAULT SIGNALS DISPLAYED DURING OPERATION:

  • warning light on indicates a fault;

  • warning light off indicates there are no faults with components that could alter the values imposed by pollution control regulations.

RECOVERY

The control unit defines the recovery settings on each specific occasion according to which components are faulty.

The recovery parameters are managed by non-faulty components.

Fiat code recognition

The moment the control unit receives the ignition MAR signal, it converses with the body computer (FIAT CODE function) to obtain the go-ahead for start-up.


Engine coolant temperature control

When the engine coolant temperature is above 105°C, the control unit:

  • reduces the quantity of fuel injected (reduces engine power);

  • controls the cooling fans;

  • switches the coolant temperature warning light on.


Control of injected fuel quantity

The control unit uses the signals coming from the sensors and the stored values to:

  • controls the pressure regulator;

  • alters the "pilot" injection time up to 3000 rpm;

  • modulates the "main" injection time.


Idling speed control

The control unit processes the signals coming from the various sensors and regulates the amount of fuel injected:

  • controls the pressure regulator;

  • modulates the injector injection times.

Within certain thresholds, the speed takes battery voltage into account.


Fuel cut-off during overrun

When the accelerator pedal is released, the control unit implements the following strategies:

  • cuts off the supply to the injectors;

  • partly reactivates the supply to the injectors before the idle speed is reached;

  • controls the fuel pressure regulator.


Control of cylinder balancing when idling

According to the signals received from the sensors, the control unit monitors torque at idle speed to ensure it is regular:

  • modulates the quantity of fuel injected into the individual injectors (injection time).


Anti-judder control;

The control unit processes the signals received by the various sensors and corrects the quantity of fuel injected in order to improve driveability and reduce jerking whilst driving by means of:

  • the pressure regulator;

  • the injector opening time.


Exhaust fumes control during acceleration

In order to restrict exhaust fumes during fast transitions, the control unit limits the amount of fuel injected according to signals received from the air flow meter and the engine speed, by means of:

  • the pressure regulator

  • the injector injection time.


Exhaust gas recirculation (e.g.r.) control

In accordance with pollution control legislation, on the basis of the engine load and the signal from the accelerator pedal potentiometer, the control unit limits the quantity of intake air, implementing the partial intake of exhaust gases, by:

  • adjusting the E.G.R. valve opening.


Maximum torque limit control

The control unit uses mapped values plotted against rpm to calculate the following:

  • the torque limit;

  • the permitted level of fumes (limit).

It compares and corrects these minimum values against other parameters:

  • coolant temperature;

  • engine rpm;

  • vehicle speed,

and controls the quantity of fuel to be injected (pressure regulator - injectors).


Maximum speed limit control

Depending on the rpm, the control unit implements two intervention strategies:

  • at 5000 rpm it cuts off the fuel, reducing the line pressure;

  • beyond 5400 rpm, it deactivates the auxiliary pump and the injectors.


Heater plugs check

The injection control unit, during the following stages:

  • start-up;

  • post start-up

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


Air conditioning system start-up check

The control unit operates the air conditioning compressor:

  • activating/deactivating it when the correct switch is pressed;

  • switching it off temporarily (about 6 secs) in the event of strong acceleration or a request for maximum power.


Auxiliary fuel pump control

Irrespective of the rpm, the control unit:

  • supplies the auxiliary fuel pump when the key is turned to ON;

  • cuts off the auxiliary pump supply if the engine is not started within a few seconds.


Cylinder position check

During each engine revolution, the control unit detects which cylinder is in the combustion phase and controls the injection sequence to the relevant cylinder.


Main and pilot injection advance check

According to the signals coming from the various sensors, including the absolute pressure sensor built into the control unit itself, the latter determines the optimum injection point, according to an internal map, based on driving comfort and emission limits.


Injection pressure closed loop check

The control unit controls the regulator to produce optimum line pressure according to engine load, which is determined by processing signals from the various sensors.


Control of electrical balance

The control unit modulates the idle speed according to the battery voltage and:

  • increases the injector injection times;

  • modulates the line pressure.


Electric fan control

Depending on the temperature of the engine coolant and the pressure of the air conditioning system coolant, the control unit controls:

  • fan activation at first or second speed.


Check on throttle closing when switching off

In order to prevent the engine juddering when it is switched off, the control unit immediately closes the inlet throttle. The throttle remains open in all other operating conditions.

Cruise control system check (where fitted)

Depending on the position of the cruise control lever, the control unit directly manages the quantity of fuel injected in order to control and maintain the vehicle speed which has been memorised.

A warning light in the dashboard, activated by the control unit, indicates system operation or deactivation status.

The cruise control is temporarily disabled:

  • by operating the brake,

  • by operating the clutch;

  • when the recall button restores the memorised speed.

The cruise control is not disabled in the event of a request from the accelerator (e.g. to overtake) and automatically restores the vehicle to the set speed as soon as the accelerator is released.

The ASR function (antispin) takes precedence over the cruise control for safety reasons.