Description of operation

DESCRIPTION OF OPERATION

The engine control unit M10controls and adjusts the entire electronic ignition and injection.

The ignition switch power (15/54) reaches pin 26 from the line protected by free fuse B35.

Pins 17 and 34 on control unit M10 are earthed.

Multiple relay J70 is powered directly by the battery from the B5 EFI maxifuse line: first contact is energised by a command signal (earth) coming from pin 4 on control unit M10 and consequently sends power to pin 35 of M10 which enables all the control unit functions.

The second contact is also powered directly by the battery from the B5 EFI maxifuse line, whereas the coil is supplied from ignition switch (15/54) through the line protected by free fuse B35; this contact is energised by a command signal (earth) coming from pin 23 on control unit M10 (safety signal that enables the fuel pump) and as a consequence sends power :

• to the electroinjector N71;
• to the coils A30,
• to the Lambda sensor heater, through the line protected by fuse B40;
• to the fuel vapours recovery solenoid valve L10, through the line protected by fuse B40;
• to the electric fuel pump N40;

The electric fuel pump N40 is earthed through the inertia fuel switch I50, which cuts off the circuit in the event of a crash to stop fuel being delivered in dangerous circumstances.

Engine control unit M10 receives the signals from the various sensors, thus keeping all the engine functioning parameters under control.

Rev sensor K46 sends information relating to engine speed to pins 11 and 28 on control unit M10 via a frequency signal: these two signals have very low intensity ad are therefore suitably shielded.

Absolute pressure sensor K48 receives its 5 V from pin 14 on the control unit and a reference earth from pin 16; it sends a frequency signal to pin 32 of the control unit, according to the pressure found.

Throttle position sensor K56 receives its 5V from pin 14 and a reference earth from pin 16; it sends a signal to pin 30 on control unit M10, proportional to the degree of throttle opening, through a potentiometer.

Engine temperature sensor K45, receives a reference earth from pin 16 on control unit M10, and sends a signal that is proportional to the engine coolant temperature to pin 13 on the control unit.

Intake air temperature sensor K42, receives a reference earth from pin 16 on control unit M10, and sends a signal that is proportional to the incoming air temperature to pin 31 on the control unit.

Heated Lambda sensor K40 sends control unit M10 information regarding the correct air-fuel mixture: the signal is sent to pin 29 on the control unit, while pin 12 sends the reference earth: these two signals have very low intensity and are therefore suitably shielded. Sensor K40 is heated with a resistor to ensure correct operation even when cold; the resistor is powered by the relay J70.

Control unit M10 controls the opening of electroinjector N71 through a special signal sent by pin 18. Injector N71 receives consent when the relay J70 opens.

Control unit M10 also controls coils A30through the command signals (earth) for the coil primary windings, whereas the secondary sends the pulse to the spark plugs: from pin 1 for the cylinder pair 1-4 and from pin 19 for cylinders 2-3.

Coil A30 primary windings receive consent whenrelay J70 opens.

Idle actuator N74 regulates the throttle by-pass line.

This has a stepper motor that controls the opening of the by-pass clearance: it is controlled by control unit M10 by means of the signals from pins 2, 3, 20 and 21 that control the various motor phases.

Fuel vapours recovery solenoid valve L10 allows the fuel vapours to pass to the engine intake, where they are added to the mixture coming into the combustion chamber. Valve L10, supplied by relay J70, is opened by the control unit when the engine is under load, through a signal from pin 22 on M10.

Control unit M10 is connected to CODE control unit M20 via serial line by pin 7 (see E7010 - ALFA ROMEO CODE).

The control unit has a self-diagnostics system that can be used by connecting the relevant connector, R20: signals reach this through pins 10 (line L) and 15 (line K) from control unit M10; the self-diagnostics system also generates the signal coming from pin 6 on M10 for the "injection fault" warning light on the E50 cluster.

Cluster E50 is supplied by ignition switch (INT) from the line protected by fuse F22on the fuse carrier B1: when this earth signal arrives, the "injection fault" warning light comes on.

Control unit M10 sends a signal from pin 23 of automatic clutch control unit (see E7040: AUTOMATIC CLUTCH); this signal is proportional to the engine revs; it is also safety signal for fuel pump.