Fiat Bravo Service Manual page 199

Engine
Fuel system
10.
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 E C U (5) receives voltage at pin 13 through pin 52 (internal earth), it enables closure of
power contacts of relay A (ECU POWER S U P P L Y 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.lf 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 automati-
cally 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 prac-
tice, 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 C O D E system.
When the ignition key is returned to S T O P 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 S T A N D - B Y memory to the E E P R O M .
NOTE Diodes D1 and D2 reduce voltage surges in the respective re/ays. Diode D3 acts against the
voltage from the low alternator charge warning light.
52
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.
P4A52CJ01
Bravo-Brava
Publication
l&iiev
no. 506.670