Controlling supply to fuel pump (page 2 of 2)

With the ignition key in MAR position, the ECU activates the electric pump for a few moments and obtains data from the various sensors.

According to information from coolant temperature sensor, the ECU commands throttle valve opening via direct current motor.The control unit recognises the start-up phase when the rpm value reading from sensor (3) exceeds 30/min.

At very low temperatures, base pulse constants increase: the injector stays open longer and a richer mixture is formed.

At very high temperatures, pulse constants are reduced to move closer to a stoichiometric ratio.

The control unit also contains an anti-flood function controlled by an internal timer that gradually reduces mixture enrichment when the engine fails to start for some reason.

During the stage following start-up,base pulse constants (ti) selected by the control unit are enriched by a function that varies according to coolant temperature and is cancelled with time.

This constant does not remain the same throughout the activation period but is reduced gradually (by a timer in the control unit)

During engine warm-upa further untimed coolant temperature-dependent enrichment takes place in addition to the enrichment that occurs after starting:

This enrichment falls gradually in inverse proportion to engine temperature.