3232842 - 1056B multi-point injection system (mpi)

General view 1, Electric fuel pump 2, Relays 3, Lambda sensor 4, Speedometer 5, Rev counter 6, Engine Check warning light 7, Detonation sensor 8, Rpm sensor 9, Fuel vapour recirculation solenoid valve 10, Butterfly casing integrated with M.D.S. 11, Injection/ignition control unit 12, Inlet manifold solenoid valve (only 1.8/2.0 T. SPARK) 13, Phase transformer 14, Injectors 15, Climate control connector 16, Diagnostic connector 17, Alfa Romeo CODE connector 18, Timing sensor 19, Ignition coils 20, Coolant temperature sensor 21, Debimeter with integral air temperature sensor

M1.5.5 fuel injection-ignition control unit

The control unit is mounted on the throttle body and withstands high temperatures.The control unit's memory is "flash EPROM", 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 cars.Pin-outA1, Flow meter sensor supplyA2, Rev counter signalA3, Fuel pump relay feedA4, Cooling fan 2nd speed contactor controlA5, N.C.A6, N.C.A7, Main relay feedA8, Supply controlled by the ignitionA9, Main relay feedA10, N.C.A11, Diagnostic connection (K line)A12, Check Engine warning lightA13, Cooling fan 1st speed contactor controlA14, N.C.A15, N.C.A16, Alfa Romeo CODE connectionA17, Supply (main relay)A18, Direct supply (battery)A19, Air conditioner compressor relay feedA20, Flow meter signalA21, N.C.A22, N.C.A23, N.C.A24, N.C.A25, N.C.A26, N.C.A27, Speedometer sensor signalA28, N.C.A29, Sensor earthA30, Air temperature sensor signalA31, Air conditioning request switchA32, N.C.A33, N.C.A34, Request to switch on fan 1st speedA35, Request to switch on fan 2nd speedA36, N.C.A37, N.C.A38, N.C.B1, Sensor earthB2, Detonation sensor signalB3, N.C.B4, Throttle position potentiometer signalB5, Coolant temperature sensor signalB6, Fuel injector control cyl. 1B7, Operation of injector for cyl. 4B8, Lambda sensor heating signalB9, N.C.B10, Operation of ignition coil for cyl. 2B11, Detonation sensor signalB12, N.C.B13, Throttle potentiometer signalB14, N.C.B15, Idle switch signalB16, Operation of injector for cyl. 3B17, Operation of injector for cyl. 2B18, Operation of ignition coil for cyl. 3B19, N.C.B20, N.C.B21, Lambda sensor reference earthB22, Engine rpm signalB23, Timing sensor signalB24, Operation of phase transformer actuatorB25, N.C.B26, Throttle actuator controlB27, N.C.B28, N.C.B29, Sensor suppliesB30, Lambda sensorB31, N.C.B32, Engine rpm sensorB33, Modular inlet manifold solenoid control B34, Fuel vapour recovery solenoid controlB35, Throttle actuator controlB36, N.C.B37, Operation of ignition coil for cyl. 2B38, Operation of ignition coil for cyl. 1

Injectors

The double-jet fuel injectors are installed on the distribution manifold.A retainer secures the fuel injectors 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.

Engine coolant temperature sensor

This is mounted on the thermostatic cup, and it measures the coolant temperature by means of an NTC thermistor with a negative resistance coefficient.The sensor is made using semiconductor technology, so if the sensor temperature increases as the coolant temperature increases, its resistive value decreases. As the variation in resistance is not linear, for the same temperature increment, it is higher for low temperatures than for high temperatures. 1, NTC resistor 2, Sensor body 3, Supply connector For operating checks.  See Test 1056B  Check on operation of engine coolant temperature sensorIn post-modification a single "twin NTC" type engine coolant temperature sensor is fitted on the thermostat which combines the function of a sender unit for the M1.5.5 control unit and the warning light in the instrument panel.

Detonation sensor

The piezoelectric knock sensor is mounted on the engine block, and it detects the intensity of vibrations caused by knocking 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 mounted on the engine block and "faces" the phonic wheel located on the crankshaft.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 phonic wheel (60-2 teeth).

The fuel injection control unit uses the rpm sensor to:

• determine the speed of rotation
• 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 range of the voltage sent to the electronic control unit provides it with the angular crankshaft speed. 1, Brass bush 2, Permanent magnet 3, Plastic sensor casing 4, Coil winding 5, Polar core 6, Toothed or phonic wheel 7, Coaxial two-wire cable or electrical connection The specified gap for obtaining correct signals, between the end of the sensor and the phonic wheel, must 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 phonic wheel. 1, Maximum magnetic flow 2, Minimum magnetic flow 3, Trend of induced alternating voltage For operating checks.  See Test 1056B  Check altitude corrector efficiency

Timing sensor

Hall effect; it is mounted on the cylinder head and "facing" the exhaust camshaft pulley.This pulley comprises a gap which enables the timing sensor to indicate the engine's timing position.The fuel injection control unit uses the timing sensor's signal to find out the TDC at the end of compression.

THROTTLE BODY INTEGRAL WITH M.D.S.

The M.D.S. actuator is fitted on the throttle body and is controlled by the fuel injection control unit.It consists of a DC motor which regulates the throttle aperture between 0° and 15°.

Two potentiometers are built into the actuator; these transmit to the fuel injection unit the following angle positions:

• 0°-15° for the idle speed
• 0°-83° for the other rpm values.

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 principle of operation 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. For operating checks.  See Test 1056B  Check efficiency of hot film air flow meter General view 1, Electric fuel pump 2, Relays 3, Lambda sensor 4, Speedometer 5, Rev counter 6, Engine Check warning light 7, Detonation sensor 8, Rpm sensor 9, Fuel vapour recirculation solenoid valve 10, Idle speed actuator 11, Injection/ignition control unit 12, Air temperature sensor 13, Phase transformer 14, Injectors 15, Climate control connector 16, Diagnostic connector 17, Alfa Romeo CODE connector 18, Timing sensor 19, Ignition coils 20, Coolant temperature sensor 21, Air flow meter

M2.10.4 fuel injection-ignition control unit

The control unit is mounted in the interior compartment on the passenger side panel.The adoption of the Alfa Romeo CODE does not allow control units to be exchanged between cars.Pin-out 1, Operation of ignition coil for cyl. 1 and 4 2, Ignition earth 3, Petrol pump contactor control 4, Constant idle speed actuator control - open 5, Evaporative solenoid control 6, Rev counter signal 7, Air flow meter signal 8, Engine timing signal 9, Speedometer signal 10, Lambda probe earth 11, Engine knock signal 12, Stabilized voltage (5V) for sensors 13, N.C. 14, Earth for fuel injectors 15, N.C. 16, Fuel injector control cyl. 3 17, Fuel injector control cyl. 1 18, Direct supply 19, Electronic shielding earth 20, Ignition coil control - cyl. 3 and 2 21, Ignition coil control - cyl. 4 and 1 22, Constant idle speed actuator control - close 23, N.C. 24, Earth for final stages 25, Operation of cooling fan 2 ^nd speed 26, Operation of cooling fan 1 ^st speed 27, "Ignition-dependent" supply 28, Oxygen quantity signal 29, N.C. 30, Electronic earth for sensors 31, N.C. 32, Air conditioner compressor relay control 33, N.C. 34, Fuel injector control cyl. 2 35, Fuel injector control cyl. 4 36, Main contactor control 38, Ignition coil control cyl. 2 and 3 39, N.C. 40, Request to switch on compressor 41, N.C. 42, N.C. 43, Request to switch on cooling fan 2 ^nd speed 44, Request to switch on cooling fan 1 ^st speed 45, Coolant temperature signal 46, N.C. 47, Connection to Alfa Romeo CODE 48, Rpm and TDC signal 49, Rpm and TDC signal 50, N.C. 51, "Engine check" warning light control 52, Timing variator control 53, Throttle valve position signal 54, Intake air temperature signal 55, Diagnostic connection (K line)

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 unrequired 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 body 2, Pintle 3, Magnetic core 4, Coil spring 5, Winding 6, Injector nose 7, Adjustable spring pusher 8, Filter 9, Electrical connection 10, Seal For operating checks see test  See Test 1056B  Check injector efficiency .

Engine coolant temperature sensor

Refer  Characteristic of working principle 1056B  multi-point injection system (mpi)

Detonation sensor

Refer  Characteristic of working principle 1056B  multi-point injection system (mpi)

Rpm sensor

Refer  Characteristic of working principle 1056B  multi-point injection system (mpi)

Timing sensor

Refer  Characteristic of working principle 1056B  multi-point injection system (mpi)

Idle speed actuator

The idle speed is controlled by means of an actuator mounted on the throttle body.It regulates the quantity of air drawn in by the engine, when the throttle valve is home.A double electromagnetic circuit ensures that the open and close controls are independent, with the advantage of very prompt adjustment.In the event of a fault, a spring brings the actuator to an intermediate position of aperture, to allow the car to reach an authorized Service Centre. For operating checks see test  See Test 1056B  Check efficiency of hot film air flow meter .

Air flow meter

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

Operation

The principle of operation 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. For operating checks see test  See Test 1056B  Check efficiency of hot film air flow meter .

Intake air temperature sensor

The intake air temperature sensor is mounted on the inlet duct.It measures the air temperature by means of an NTC (negative resistance coefficient) thermistor, which reduces the resistance as the temperature increases. For operating checks see test  See Test 1056B  Check intake air temperature sensor operation .

Throttle position switch

Mounted on the throttle body, its moving part is controlled directly by the throttle spindle. For operating checks see test  See Test 1056B  Check on operation of throttle casing throttle position switch .