198002696 - INTRODUCTION - DIESEL INJECTION PRESSURE PUMP ELECTRONIC CONTROL
DESCRIPTION OF COMPONENTS
Injection control unit (EDC 16C39 common rail)
This is fitted in the engine compartment on the right side. It is a flash EPROM type control unit, i.e. it can be externally reprogrammed without adjusting the hardware.The injection control unit incorporates the absolute pressure sensor.PIN OUT
RPM SENSOR
Specifications
It is fitted on the cylinder block, facing the phonic wheel on the crankshaft.It is inductive, i.e. its operation is determined by magnetic field changes generated by the teeth passing in front of a phonic wheel (60-2 teeth).The injection control unit uses the rpm sensor signal to:
- determine the engine rotation speed
- determine the crankshaft angular position.
Operation
The changeover from full to empty determined by the presence or absence of a gap brings about a magnetic flux change sufficient to generate an induced alternating voltage proportional to the number of teeth on the ring (or phonic wheel).The frequency and amplitude of the voltage sent to the electronic control unit provides it with details of crankshaft angular speed.
CAM ANGLE SENSOR
Specifications
This Hall effect sensor is fitted on the cylinder head, facing the camshaft drive pulley.A tooth on the pulley allows the timing sensor to indicate the engine timing position.The injection control unit uses the timing sensor signal to identify T.D.C. at the end of compression.
Operation
A current-carrying semiconductor layer submerged in a normal magnetic field (with force lines at right angles to the direction of the current) generates a potential difference known as a Hall voltage at the terminals of the semiconductor.If the intensity of the current remains constant, the generated voltage depends on magnetic field intensity alone. Periodic changes in magnetic field intensity are sufficient to generate a modulated electrical signal whose frequency is proportional to the speed at which the magnetic field changes. To produce this change, a tooth on the inner part of the pulley periodically moves close to the sensor.
INTAKE AIR TEMPERATURE AND EXCESS PRESSURE SENSOR
Specifications
The excess pressure and intake air temperature sensor is an integral component designed to measure the pressure and the temperature of the air inside the intake manifold.It is fitted on the intake manifold and has the task of informing the injection control unit to:
- regulate the pressure of the variable geometry turbine in order to ensure optimum engine performance in all operating conditions.
- regulate fuel injection duration.
ENGINE COOLANT TEMPERATURE SENSOR
Specifications
This is fitted on the thermostat and detects coolant temperature by means of a dual NTC thermistor with negative resistance coefficient.One NTC thermistor sends a signal to the injection control unit, whilst the other sends a signal to the temperature gauge and the warning light on the instrument panel.
AIR FLOW METER WITH BUILT-IN AIR TEMPERATURE SENSOR
Specifications
The air flow meter is located on the air intake sleeve and is a hot film type meter.
 | The air flow meter cannot be disassembled. |
Operation
This component works on the basis of a heated membrane positioned within a measurement channel that carries intake air into the engine.The hot film membrane is maintained at a constant temperature (about 120°C higher than the incoming air temperature) by the heating coil.The air mass that flows through the measurement channel tends to remove heat from the membrane. A certain amount of current must therefore flow through the heater coil in order to maintain the membrane at a constant temperature.This current is measured by a special Wheatstone bridge.The current is therefore proportional to the flowing air mass. | The air flow meter measures the air mass (not the volume) directly to eliminate problems of temperature, altitude, pressure etc. |
FUEL PRESSURE SENSOR
Specifications
It is fitted at the end of the common rail and its function is to provide the injection control unit with a feedback signal to enable it to:
- modulate injection pressure;
- regulate fuel injection duration.
ACCELERATOR PEDAL POTENTIOMETER
Construction specifications
The sensor consists of a case secured to the accelerator pedal; the case contains an axially-located shaft connected to two potentiometers: a main one and a safety one.A coil spring on the shaft ensures the correct amount of resistance to pressure while a second spring ensures return following release.
Operation
The accelerator pedal position is converted into an electrical voltage signal and sent to the injection control unit by the potentiometer connected to the pedal.The accelerator pedal position signal is processed together with the information relating to the engine rpm in order to obtain the injection times and the pressure.MOTORISED THROTTLE BODY (only for versions with DPF)
The electrical throttle body is a system that includes both the control logics and the activation logics of the electric motor for moving the throttle valve.The system is operated by means of a PWM-type signal, which is processed by the electronics of the actual component. The position of the throttle valve is controlled as a result.The motorised throttle casing carries out the following two functions:- management of the shut-off stage- control the exhaust gas temperature by reducing the intake duct cross-section.Operating specificationsTemperature interval: between - 40 °C and + 140 °CInput signal: PWMInput signal frequency: 262.2 Hz +/- 3%Signal for diagnosis: PWMFrequency of signal for diagnosis: between 20 and 90 Hz +/- 5%Supply voltage: 14 V