125000303 - 1080E EVAPORATION CONTROL SYSTEM

OPERATION

Vapours from the fuel tank flow through two float valves (1) to the separator (2). The vapours condense in the separator and drop into the tank.

Multifunction valves

The functions of the multifunction valves are as follows:

  • tank pressurisation
  • tank ventilation
  • retention
  • seal in the case of roll-over.
TANK PRESSURIZATIONWhen tank pressure exceeds a set level, it overcomes spring resistance and allows the valve to rise so that fuel can flow out toward the canister.The valve re-closes when the pressure returns to within specified limits.RETENTION

Under specific vehicle operating conditions, a vacuum develops in the tank due to:

  • thermal changes
  • fuel consumption.
In this case, the valve''s function is to restore pressure in the tank by admitting air.A fault in this function may lead to juddering or stalling because not enough fuel can reach the pump.SEAL IN THE CASE OF ROLL OVERThe roll-over function prevents fuel emerging from the tank if the vehicle rolls over or tilts too far to one side.During normal vehicle operation (cornering, acceleration, braking etc.), the fuel may slop over into the canister.The high roll over sensitivity prevents this slopping; the roll over closing angle is less than 33°.

Canister

This is fitted to the right front wheel arch and consists of an activated carbon filter element that absorbs fuel vapours from the separator.A one-way valve admits outside air (flushing air) during vapour intake.

Fuel vapour solenoid valve

This is fitted on the lower part of the modular intake manifold and is controlled by the injection control unit.The solenoid allows fuel vapours stored in the canister to flow through to the engine intake.If deactivated, the solenoid remains in open position. At key-ON, it closes ready for operation.Electromagnet (1) is excited and attracts plunger (2) that overcomes the load of spring pack (3) to close orifice (4) and prevent fuel vapours from passing through.

SAFETY AND VENTILATION VALVE

Operation

This valve is built into the fuel filler cap and performs as follows, depending on fuel pressure in the tank.Excess pressure in tankWhen tank pressure exceeds the specified value, it acts on plate (2) and overcomes the load on spring (1) so that excess vapours can be vented outside.Vacuum in reservoirWhen excess pressure builds up in the tank due to fuel consumption, this overcomes the load on spring (4) and moves valve (3) to admit air.