Other control functions

OTHER CONTROL FUNCTIONS

Starting control

When the engine is started the ECM provides a rich mixture by increasing fuel injector duration.

Fuel pump control

When the ignition switch is initially turned on, the ECM supplies a ground signal to the fuel relay which supplies current to the fuel pump for two seconds to pressurise the fuel system.

When the engine is running, the ECM provides a ground signal to the fuel relay which supplies current to the fuel pump.

When the engine is not running and the ignition is ON, the ECM cuts the earth signal to the fuel relay which cuts the current to the fuel pump.

If the engine speed falls below a predetermined level the fuel pump is shut off to improve safety in the event of an accident.

Fuel cut-off control

During deceleration with the throttle valve closed, current to the injectors is cut off to improve fuel economy at speeds over set rpm.

Fuel cut-off action also takes place when engine speed exceeds set rpm regardless of the position of the throttle valve to protect the engine from over-revving.

Purge cut-off solenoid valve

When the coolant temperature is below predetermined temperature, the ECM supplies a signal to the purge cut-off solenoid valve which cuts vacuum to the purge control valve.

Lock-up control solenoid valve

The speed and throttle position sensor inputs to the ECM are used to send an on/off voltage signal to the lock-up control solenoid valve for precise timing of the torque converter lock-up system.

Fuel Pressure Regulator

The fuel pressure regulator maintains a constant fuel pressure to the injectors. When the difference between the fuel pressure and the manifold pressure exceeds a predetermined limit, the diaphragm is pushed upwards and the excess fuel is fed back into the fuel tank through the return line.

When the coolant temperature or intake air temperature exceeds a predetermined limit, the pressure regulator cut-off solenoid valve cuts vacuum to the pressure regulator, to ensure high fuel pressure to the injectors and prevent vapour lock.

The fuel rail supplies fuel to the injectors which are operated by the ECM The injectors are solenoid operated and have a pintle tip enabling fuel to be atomised efficiently. When the ECM completes the earth through the solenoid coil, the valve lifts and pressurised fuel is injected into the intake ports.

PGM-Fi Main Relay

The main fuel relay actually contains two individual relays.

One relay is energised whenever the ignition is on and this supplies battery voltage to the ECM, power to the injectors and power for the second relay.

The second relay energises for two seconds when the ignition is switched on and when the engine is running, and supplies power to the fuel pump.

Oxygen sensor

An oxygen sensor is fitted to the engine exhaust manifold, to detect the amount of oxygen in the exhaust gases and send signals to the ECM. The ECM interprets the signals and varies the duration during which the fuel is injected accordingly.