Diagram Showing Fuel Anti-Evaporation Circuit - Fiat Bravo Service Manual

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Bravo ft 20v

D I A G R A M SHOWING F U E L A N T I - E V A P O R A T I O N C I R C U I T

1. Fuel vapour cut out solenoid valve

2. Charcoal filter

3. Multi-purpose valve

4. Fuel vapour separator

The anti-evaporation system is designed to prevent the fuel vapours, consisting of the lightest particles

of hydrocarbons w h i c h form in the tank, f r o m being discharged into the atmosphere.

The system works, above all, at high outside temperatures, w h e n the temperature of the fuel increases

and consequentlythe tendency towards evaporation increases; in this situation, there is an increase in

the pressure inside the tank ( 7 ) .

In particular, even w h e n the tank (7) is full, w h e n the vehicle is stationary, the float valves (6) remain

open, as they are located higher than the breather pipe and therefore they allow the vapours to reach the

separator (4), from where, w h e n they condense, they mainly return to the tank ( 7 ) .

In the case of spillage whilst driving or if the vehicle overturns, the float valves (6) close, preventing fuel

from escaping.

When the pressure inside the tank reaches approximately 3 0 - 4 0 mbar, the multi-purpose valve (3)

opens and the fuel vapours reach the charcoal filter ( 2 ) . The valve (3) also allows an intake of air into

the tank through the charcoal filter, for example after the level of the fuel decreases w i t h the consequent

vacuum created inside the tank.

With the engine running, the control unit (8) controls the fuel vapour cut out solenoid valve (1), w h i c h al-

lows the intake of vapours by the engine and the consequent scavenging of the charcoal filter ( 2 ) .

If, as a result of the malfunction of a component, the pressure inside the tank increases to dangerous lev-

els, the safety valve ( 5 ) , located near the cap, allows the pressure to be discharged outwards. If neces-

sary, this valve can open in the other direction to ventilate the tank and prevent the vacuum reaching ex-

cessive levels.

5. Safety and ventilation valve

6. Float valve

8. Injection/ignition control unit