2888234 - 1080E evaporation control system

The vapours coming from the tank through the two multi-purpose valves (1) are sent to the separator (2).The condensed vapours in the separator fall back into the tank.Uncondensed vapours are sent through the multi-purpose valve and the pipe (3) to the canister (4), where they are absorbed and stored by the activated charcoal.The vapours flow to the inlet manifold through the solenoid valve (5) operated by the injection control unit.
1, Float valve 2, Petrol vapour separator 3, Multi-purpose valve 4, Canister 5, Vapour cut out solenoid valve 6, Engine control unit

FLOAT VALVE

These valves are used for carrying out the following functions:

  • preventing the escape of liquid fuel in the case of an accident where the vehicle overturns;
  • allowing the breathing of fuel vapours from the tank to the separator and therefore to the activated charcoal filter;
  • allowing the ventilation of the tank if there is a vacuum inside.
This valve consists of a body (1) and a float/needle valve (2).The operation of the valve can be summarized in the following cases in relation to how full the fuel tank is.

Tank full

If the tank is full, the float (2) shutters the port (3) preventing the liquid fuel from reaching the separator.

Intermediate fuel level

If the level of the fuel in the tank decreases, the float (2) descends and rests via the side tabs (4) on the slits in the valve body (1) opening the port (3), which can be reached by the gases through the ring section between the float (2) and the valve body (1) inner seat. This allows the fuel vaopurs to escape from the tank and reach the separator and the activated charcoal filter, or through the same circuit to ventilate the tank when the pressure inside is below the pressure outside.

Seal in the event of roll-over

If the vehicle overturns, irrespective of how full the tank is, the float (2), weighing down with its own weight and that of the fuel on the port (3), prevents the dangerous flow of fuel to the activated charcoal filter and the consequent risk of the vehicle catching fire.

CANISTER

Mounted in the engine compartment, this consists of an activated-charcoal filter element which absorbs the fuel vapours coming from the separator.A one-way valve allows the entry of external (scavenging) air which comes into contact with the carbon granules, removing the petrol vapours and directing them through the outlet (1) to the inlet manifold when the fuel vapour solenoid valve is open.
1, From the multi-purpose valve 2, To the inlet manifold 3, One-way scrubbing valve 4, Fuel vapour solenoid valve

FUEL VAPOUR SOLENOID VALVE

Specifications

This is fitted on the canister mounting and is controlled by the fuel injection control unit.The function of the solenoid is to allow the passage of fuel vapours stored in the engine intake canister.If there is no supply the solenoid valve is in the closed position, preventing the fuel vapours from enriching the mixture too much.The solenoid valve is operated by the control unit according to a specific strategy (see 1056)When the electro-magnet (3) is energized, it attracts the valve core (1) which overcomes the spring (2) loading, placing the activated charcoal filter in contact with the inlet manifold air.

MULTI-PURPOSE VALVE

The valve functions are:

  • pressurization of the tank
  • retaining
  • seal in the event of roll-over

Pressurizing the tank

The tank is maintained at a pressure of 30-45 mbar by means of a fluorosilicone rubber valve, which rests on a sealing edge.The valve is supported by a stainless steel plate and counteracted by a spring.When the pressure in the tank exceeds the specified value, it overcomes the resistance of the spring and the valve is able to rise, allowing vapours to flow to the canister. When the pressure returns to the correct limits, the valve closes again.

Retaining

Under particular driving conditions, a vacuum could be created in the tank because of:

  • temperature changes
  • fuel consumption.
In this case, the valve's function is to restore the pressure of the tank by allowing air in.A fault in this function could cause the engine to miss or stall, because of difficulties in supplying the fuel pump.This function is carried out by the "goose beak" valve formed directly out of the fluorosilicone rubber.

Seal in the event of roll-over

The roll-over function prevents fuel from leaking from the tank if the vehicle overturns or is on a very steep slope.During normal driving of the vehicle (bends, acceleration, braking, etc.), the fuel is shaken up and may spill into the canister.The high sensitivity of the roll-over prevents this spillage.The roll-over closure angle is less than 33°.

SAFETY AND VENTILATION VALVE

This valve is built into the fuel filler cap, and it carries out the following functions, depending on the pressure present in the tank:

  • it discharges excessive pressure which forms inside the tank (safety function); the pressure acts on the plate (2) and, overcoming the load of the spring (1), allows excess vapours to be discharged outside.
  • it allows external air to flow into the tank when an excessive vacuum is created in the tank, following the consumption of fuel (ventilation function). In this case, when the vacuum exceeds the load of the spring (4), it moves the valve (3), allowing air to enter.