Removing-refitting

A dual relay specifically for automotive applications ensures the battery voltage reaches the system. This electrical device consists of a single container containing two special normally open relays whose task is to supply the electronic control unit (section A, control unit supply) and main injection-ignition power circuits (pump, coils etc.) (section B).

When ignition key is in MAR position “Services 15/54”, excitation winding of relay (9) on pin 12 and ECU on pin 13 are activated.

As soon as ECU (5) receives voltage at pin 13 through pin 52 (internal earth), it enables closure of power contacts of relay A (ECU POWER SUPPLY section) to ensure the battary is supplied at pin 35 through fuse (8); it then enables closure of power contacts of relay B in order to earth pin 7 and ensure a power supply to pump (11) and the other sensors and actuators making up the injection system.

The fuel pump must be activated before starting up the engine to ensure that the fuel system is already under a pressure of 3 ± 0.5 bar.If starting does not not take place with the ignition key in MAR position, the electronic control unit (5) deactivates section of relay (9) pin 7 (pump-components) and automatically stops the pump (11). Timed enablement lasts about 10 sec.

For safety reasons, the ECU (5) activates a control strategy for pump (11) based on engine rpm. In practice, the ECU (5) deactivates section of relay (9) pin 7 in order to cut off supply to the pump (11) when engine rpm drops below a minimum memorised threshold, if the engine stalls with the ignition on or if the start-up code is not recognised by the Fiat CODE system.

When the ignition key is returned to STOP position, the electronic control unit maintains section A of the dual relay excited for about 90 seconds before cutting off its power supply (time taken to transfer data from RAM STAND-BY memory to the EEPROM.

NOTE Diodes D1 and D2 reduce voltage surges in the respective relays. Diode D3 acts against the voltage from the low alternator charge warning light.

Removing-refitting

The dual relay is fitted on a bracket against the rear wall of the engine bay. Proceed as follows to remove-refit:

Remove the protective cover.
Disconnect electrical connection and remove the dual relay.