Other control functions

Other control functions

Starting control

When the engine is started the E.C.U. provides a rich mixture and a signal to the ignition.

Fuel pump control

When the ignition switch is initially turned on, the E.C.U. 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 E.C.U. 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 E.C.U. 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.

Air conditioner (A/C) compressor clutch relay

When the E.C.U. receives a demand for cooling from the air conditioning system (clutch relay), it delays the compressor from being energized and enriches the mixture to ensure a smooth transition to the air conditioning mode.

Purge cut – off solenoid valve

When the coolant temperature is below predetermined temperature, the E.C.U. supplies a signal to the purge cut – off solenoid valve which cuts vacuum to the purge control valve.

Resonator control solenoid valve

When the engine speed is above 3000 rpm, the E.C.U. supplies current to the resonator control solenoid valve. This opens the solenoid valve sending intake manifold vacuum to the resonator diaphragm and opens the resonator flap.

Lock – up control solenoid valve (automatic gearbox)

The speed and throttle angle sensor inputs to the E.C.U. 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.