244000419 - CONSTRUCTION SPECIFICATIONS

The system used for tank ventilation is closed loop type.This system prevents fuel vapours that form inside the tank and in the fuel system from discharging into the atmosphere and thus releasing their polluting load of light hydrocarbons (HC).Diagram showning fuel evaporation control system and location of components on vehicleThe system consists of: tank (1) with a filler cap containing a tank ventilation and safety valve; fuel vapour separator (2) fitted with multifunction valve (8); activated carbon filter (or trap) (7); carbon filter scrubbing control solenoid (5) that is controlled by injection-igntion control unit (3) and controls the vapour flow to intake manifold (6).The system operates when fuel temperature increases if the vehicle is left parked for long periods with high outdoor temperatures (because the tank is no longer cooled by the ventilation caused by the speed of vehicle motion) and pressure builds up inside the tank. This increase may occur with medium-low fuel levels or with a full tank and in particular:with the tank full, multifunction valve (8) is closed and fuel cannot therefore flow to filter (7) and thus spoil the activated carbon by direct contact. If pressure inside the tank increases beyond a certain limit, the safety valve on the cap will open to allow the excess fuel to discharge outside. If necessary, the valve may open in the opposite direction to ventilate the tank if a vacuum has built up inside.with medium-low fuel levels, multifunction valve (8) allows fuel vapours to flow to filter (7) when a certain pressure is exceeded. Here they are absorbed by activated carbon granules. These vapours then reach the intake manifold when the electronic control unit controls opening of solenoid (5).

ACTIVE CHARCOAL FILTER

It consists of carbon granules that trap fuel vapours entering intake (2).Warm flushing air enters intake (1) and flows over the carbon granules to remove fuel vapours and carry them towards outlet (3) and then on to the cut-off valve.Air entering intake (1) may also be drawn in by the vacuum in the tank to ventilate the tank.

MULTIFUNCTION VALVE

This valve performns various functions, namely:prevent liquid fuel emerging if the tank is too full or in the case of an accident that involves the car overturning.allow fuel vapours to vent toward the activated carbon filter;allow tank ventilation if a vacuum builds up inside.The multifunction valve operates as follows:a) Under normal operating conditions, pressure excercised by fuel vapours overcomes the valve closure load and allows vapours to reach the carbon filter, to which the valve is connected via port (3) through ventilation holes (1) and (2).b) If the fuel level drop in the tank creates a vacuum inside the tank, the valve opens to ventilate the tank through the carbon filter.c) if the vehicle rolls over, the valves seals to prevent a dangerous outflow of fuel to the intake manifold and the consequent risk of fire.

FUEL VAPOUR SEPARATOR

Fuel vapours from the tank reach the fuel separator positioned inside the engine bay through three ducts (1), (2) and (3). A portion of the fuel vapours condenses and returns to the tank via duct (2) while the remaining vapours emerge from the upper duct (4) through multifunction valve (5).

FUEL VAPOUR CUT-OFF SOLENOID (CARBON FILTER SCRUBBING)

This valve controls the amount of fuel vapours taken up by the active carbon filter and directed to the intake manifold via the injection-ignition electronic control unit.When the key is turned ON, the normally open solenoid is activated and closes to enter operating mode. Electromagnet (6) is excited and attracts plunger (4) that overcomes the load of spring pack (3) to close orifice (5) and prevent vapours from entering.Check valve (2) prevents vapours in the filter from saturating the intake manifold with the engine off and causing loss to the atmosphere and warm starting difficulities.

The valve should be positioned so that the arrow on the case faces the intake manifold.