Anti-Evaporation System Components; Multi-Purpose Valve - Fiat Bravo Service Manual

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A N T I - E V A P O R A T I O N S Y S T E M C O M P O N E N T S

This valve is used t o carry out various functions, namely:

- to prevent the f l o w of liquid fuel if the tank is too full or if the vehicle overturns in the case of an acci-

- to allow the breathing of the fuel vapours towards the active charcoal filter;

- to allow the ventilation of the tank if there is a vacuum inside.

The valve consists of a float body ( 2 ) , a heavy ball ( 3 ) , a plate thrust against the valve body by a spring

(5) and a shim (8) thrust against the plate (4) by the spring ( 9 ) . The operation of the multi-purpose

valve can be summed up in the following cases, depending on h o w full the fuel tank is:

if the tank is full, the float (2) shutters the port (1) preventing the liquid fuel from reaching the active

charcoal filter preventing it from being damaged;

jf the level of the fuel in the tank decreases, the float (2) goes d o w n and rests on the ball (3) open-

ing the port ( 1 ) ; w h e n the pressure exerted by the fuel vapours on the plate (4) overcomes the

spring (5) loading, a ring section opens between the actual plate and the valve body, allowing the

fuel vapours to come out of the duct (6) and reach the active charcoal filter;

if the level of the fuel in the tank decreases to such an extent as to produce a vacuum inside the tank,

this acts on the shim (8) and, overcoming the spring (9) loading, recalls it downwards allowing the

ventilation of the tank through the port ( 7 ) .

if the vehicle overturns, irrespective of how full the tank is, the ball ( 3 ) , weighing d o w n on the float

(2), pushes it against the port (1) preventing the escape of fuel w h i c h w o u l d be dangerous and cre-

ate a fire hazard.

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