Multi-point injection system (mpi)

Description 1056B

3.2 V6

CONSTRUCTION FEATURES

General view

1 - Electric fuel pump

2 - Relays

3 - Lambda sensors upstream of catalytic preconverters

4 - Lambda sensors downstream of catalytic preconverters

5 - Speedometer

6 - Rev counter

7 - Engine Check warning light

8 - Timing sensor

9 - Climate control connector

10 - Diagnostic connector

11 - Alfa Romeo CODE connector

12 - Injection/ignition control unit

13 - Injectors

14 - Coolant temperature sensor

15 - Rpm sensor

16 - Air flow meter with air temperature sensor

17 - Ignition coils

18 - Knock sensors

19 - Fuel vapour recirculation solenoid valve

20 - Accelerator pedal with built-in potentiometer.

21 - Clutch pedal switch

22 - Brake pedal switch

23 - Throttle body integral with D.V.L.

24 - CAN line

ME7.3.1 injection/ignition control unit

The control unit is fitted in the engine compartment, on the intake chamber.

The control unit memory is the 'flash EPROM type, i.e. reprogrammable from the outside without intervening on the hardware.

The adoption of the Alfa Romeo CODE does not allow control units to be exchanged between vehicles.

The control unit implements the self-learning mode in the following conditions:

• installation of new injection control unit,
• installation of a new throttle body actuator integratd with D.V.L.
• removing/refitting or replacement of rpm sensor/phonic wheel, for recognizing misfire.

PIN-OUT

F1 - Not connected

F2 - Fuel vapour recovery solenoid control

F3 - Alfa Romeo CODE connection

F4 - Not connected

F5 - Not connected

F6 - Compressor engagement request

F7 - Supply for accelerator pedal potentiometer

F8 - Signal for potentiometer - 1 accelerator pedal

F9 - Quadrinary - Fan 1st speed request

F10 - Cruise Control ON/OFF

F11 - Not connected

F12 - CAN-L line

F13 - Compressor relay control

F14 - Not connected

F15 - Direct power supply

F16 - Ignition-operated power supply, via main relay

F17 - Not connected

F18 - Cruise Control warning light

F19 - Engine coolant overheating warning light

F20 - Preparation for Flash Programming

F21 - Not connected

F22 - Fuel level sensor

F23 - Not connected

F24 - Earth for potentiometer - 1 accelerator pedal

F25 - Earth for potentiometer - 2 accelerator pedal

F26 - Brake lights switch

F27 - Brake lights

F28 - Not connected

F29 - CAN -H line

F30 - Fuel pump relay control

F31 - Main relay activation

F32 - Ignition-operated power supply, via main relay

F33 - Not connected

F34 - Engine coolant warning light

F35 - Rev counter signal

F36 - Not connected

F37 - Not connected

F38 - Not connected

F39 - Not connected

F40 - Signal for potentiometer - 2 accelerator pedal

F41 - Quadrinary - fan 2nd speed request

F42 - Cruise Control Resume

F43 - Cruise Control SET +

F44 - Not connected

F45 - Not connected

F46 - Injection warning light

A47 - +15 ignition-operated power supply

A48 - Supply controlled by ignition, via main relay

F49 - Not connected

F50 - Fan 1st speed control

F51 - Not connected

A52 - Fuel consumption signal

F53 - Diagnostic connection (K line)

F54 - Air temperature sensor signal

F55 - Not connected

F56 - Supply for accelerator pedal potentiometer

F57- Air flow meter signal

F58 - Cruise Control SET -

F59 - Switch on clutch pedal

F60 - Not connected

F61 - Not connected

F62 - Fan 2nd speed control

F63 - Air flow meter supply

F64 - Not connected

M1 - - Throttle body motor earth

M1 - Lambda sensor heater (pre-cat. 2)

M3 - Operation of injector for cyl. relay

M4 - Not connected

M5 - Not connected

M6 - Knock sensor reference earth 2

M7 - Lambda sensor reference earth 2)

M8 - Not connected

M9 - Not connected

M10 - Engine RPM sensor

M11 - Not connected

M12 - Lambda sensor reference earth (post-cat 2)

M13 - Not connected

M14 - Cylinder 3 coil operation

M15 - Cylinder 2 coil operation

M16 - Cylinder 1 coil operation

M17 - Throttle body motor supply

M18 - Lambda sensor heater (post-cat. 2)

M19 - Operation of injector for cyl. relay

M20 - Operation of injector for cyl. 3

M21 - Not connected

M22 - Knock sensor 1

M23 - Lambda sensor signal (pre-cat. 1)

M24 - Potentiometer - 1 throttle body

M25 - Engine coolant temperature

M26 - Sensors reference earth

M27 - Not connected

M28 - Lambda sensor signal (post-cat. 1)

M29 - Not connected

M30 - Cylinder 6 coil operation

M31 - Cylinder 5 coil operation

M32 - Cylinder 4 coil operation

M33 - Throttle body motor earth

M34 - Lambda sensor heater (pre-cat 1)

M35 - Operation of injector for cyl. 4

M36 - Operation of injector for cyl. 6

M37 - Not connected

M38 - Knock sensor 2

M39 - Lambda sensor signal (pre-cat. 2)

M40 - Throttle body potentiometer 2

M41 - Not connected

M42 - Timing sensor signal

M43 - Not connected

M44 - Lambda sensor signal (post-cat. 2)

M45 - Not connected

M46 - Not connected

M47 - Not connected

M48 - Not connected

M49 - Throttle body motor supply

M50 - Lambda sensor heater (post-cat. 1)

M51 - Not connected

M52 - Operation of injector for cyl. 5

M53 - Not connected

M54 - Knock sensor 1 reference earth

M55 - Lambda sensor reference earth 1)

M56 - Not connected

M57 - Not connected

M58 - Throttle body potentiometer supply

M59 - Engine rpm sensor

M60 - Lambda sensor reference earth (post-cat. 1)

M61 - Not connected

M62 - Not connected

M63 - Not connected

M64 - Not connected

INJECTORS

The single-jet fuel injectors are installed on the distribution manifold and are pressed by the manifold itself into their respective seats in the inlet ducts.

A retainer secures the fuel injector to the distribution manifold, and two O-rings ensure the seal.

The fuel injectors are responsible for delivering the necessary quantity of fuel to the engine.

They are 'all or nothing' devices, as they can remain in only two stable states, i.e. open or closed. They allow fuel to pass when they are open, while they block delivery when they are closed.

Operation

They basically consist of a nozzle controlled by a solenoid and a return spring (4).

In the rest position, the pintle (2), which is joined to the core (3), is pushed by the spring onto the injector nose (6), thus closing the hole, ensuring a seal and preventing the undesired emergence of fuel.

As soon as the winding (5) is energized, the core is attracted, and it compresses the spring thus opening the hole of the nozzle and allowing fuel to emerge.

Considering the physical characteristics of the fuel (viscosity, density) and the pressure drop (via the pressure regulator) to be constant, the quantity of fuel injected depends only on the fuel injector opening time.

The winding energization time is normally indicated as 'fuel injection time'.

1 - Injector case

2 - Pintle

3 - Magnetic core

4 - Coil spring

5 - Winding

6 - Injector nose

7 - Adjustable spring loader

8 - Filter

9 - Electrical connection

10 - Sealing ring

ENIGINE COOLANT TEMPERATURE SENSOR

It is fitted on the thermostatic cup and measures the temperature of the coolant by means of an NTC thermistor which has a negative resistance coefficient.

The sensor is produced using semiconductor technology, so if the temperature of the sensor increases as the temperature of the coolant increases, the resistance decreases.

As the variation in resistance is not linear, for the same temperature increment, it is higher for low temperatures than for high temperatures.

DETONATION SENSORS

The piezoelectric type detonation sensors are fitted on the cylinder block/crankcase, between the two heads, and measure the intensity of the vibrations caused by the detonation in the combustion chambers.

The piezoelectric crystal forming the sensor detects the vibrations generated at a frequency of between 12 and 16 kHz, and transforms them into electrical signals sent to the fuel injection control unit.

RPM SENSOR

It is fitted on the engine block, where it faces the phonic wheel located on the flywheel.

It is of the inductive type, i.e. it functions by means of the variation in the magnetic field generated by the passage of the teeth of the flywheel (60-2 teeth).

The engine management control unit uses the rpm sensor to:

• – determine the rotation speed;
• determine the angle of the crankshaft.

Operation

The passage from full to empty, due to the presence or absence of the tooth, causes a variation in the magnetic flow which is sufficient to generate an induced alternating voltage, resulting from the count of teeth located on a ring (or phonic wheel).

The frequency and amplitude of the voltage sent to the electronic control unit give the latter the measurement of the speed of the front wheels.

1 - Brass bush

2 - Permanent magnet

3 - Plastic sensor casing

4 - Coil winding

5 - Polar core

6 - Phonic wheel

7 - Two-wire coaxial cable

The distance (gap) for obtaining correct signals, between the end of the sensor and the flywheel, should be between 0.8 and 1.5 mm.

This gap is not adjustable, so if a value outside the tolerance range is measured, check the condition of the sensor and the flywheel.

1 - Maximum magnetic flow

2 - Minimum magnetic flow

3 - Induced alternating voltage trend

TIMING SENSOR

Hall effect; it is mounted on the cylinder head and faces a disc on the rear part of the right cylinder head exhaust end camshaft.

The disc contains a peg which allows the sensor to signal the engine timing position.

The engine control unit uses the timing sensor signal for recognizing T.D.C. at the end of compression for a quick start.

Operation

A semiconducting layer, through which current passes, immersed in a perpendicular magnetic field (force lines perpendicular to the current direction), generates at its ends a difference in potential known as Hall voltage.

Whilst the disc (1) rotates, when the tooth (3) passes over the sensor (2), it blocks the magnetic field with a consequent 'low' output signal.

Conversely, after the tooth (3) passes the sensor (2), the signal becomes 'high'.

Consequently the high signal alternates with the low signal every two engine revolutions, to be precise when cylinder no. 1 is 58° before TDC.

1 - Camshaft disc

2 -Timing sensor

3 - Tooth

ACCELERATOR PEDAL WITH BUILT-IN POTENTIOMETER

The sensor consists of a casing, secured to the accelerator pedal mount, which contains a shaft, in an axial position, connected to two potentiometers: one main one and one safety one.

The engine control unit implements the following recovery strategies:

• if there is a fault with one of the two potentiometers, a throttle opening of up to 25% is allowed for a long period
• if both of the potentiometers fail completely, or one potentiometer and the brake pedal switch fail, the throttle opening is excluded.

There is a coil spring on the shaft which guarantees the correct resistance to the pressure whilst a second spring ensures the return on release.

Operation

The position of the accelerator pedal is transformed into an electrical voltage signal and is sent to the fuel injection control unit by the potentiometer connected to the accelerator pedal.

The accelerator pedal position signal is processed together with the information relating to the rpm, to obtain the fuel injection times and relevant pressure.

THROTTLE BODY WITH DVL

It is fitted on the inlet chamber and regulates the quantity of air drawn in by the engine.

According to the signal coming from the accelerator pedal potentiometer, the injection control unit controls the opening of the throttle by means of a direct current motor integrated in the throttle body integrated with D.V.L.

The throttle opening takes place between 0° and 80° therefore including the idle adjustment.

The throttle body integral with D.V.L. is equipped with two potentiometers integrated so that one controls the other and viceversa.

If both the potentiometers fail or there is no supply, depending on the position of the accelerator pedal, the control unit reduces the drive torque:

• fully depressed, it cuts off the supply to one or more pistons, until a maximum speed of 2500 rpm is reached.
• in intermediate positions, it cuts off the supply to one or more pistons, until a speed below 2500 rpm is reached.

If the throttle body integrated with D.V.L. or the injection control unit or the air chamber is replaced then the self-learning procedure must be carried out.

Air flow meter

The flow meter is located on the air inlet duct and is of the 'hot film' type.

The intake air temperature sensor is built into the flow meter.

1 - Covers

2 - Electronic card

3 - Sensor

4 - Support plate

5 - Support

6 - O-ring

7 - Temperature sensor

The air flow meter cannot be dismantled.

Operation

The operating principle is based on a heated diaphragm located in a measuring duct through which the intake air entering the engine flows.

The hot film diaphragm is kept at a constant temperature (about 120°C above the incoming air temperature) by the heating resistor.

The air mass passing through the measuring duct tends to draw heat from the diaphragm, so to keep the latter at a constant temperature, some current must flow through the resistor.

This current is measured by a suitable Wheatstone bridge.

The current is therefore proportional to the mass of flowing air.

The flow meter directly measures the air mass (not volume), thus eliminating problems of temperature, altitude, pressure, etc.