Tank pressurisation

The multifunction valve is located on the fuel tank and performs the following functions:

• tank pressurisation
• ventilation
• seal if the car rolls over

Tank pressurisation

Tank pressurisation is maintained at a level between 55 and 75 mbars by means of a valve mounted on a sealing rim.

The valve is supported by a steel plate and held in place by a spring.

When tank pressure exceeds a specified level, it overcomes spring resistance and allows the valve to rise so that vapours can flow out.

When the pressure returns to within specified limits, the valve closes again

Ventilation

Under certain car service conditions, a vacuum may build up in the tank due to the effect of:

• heat changes;
• fuel consumption

in this case, the valve's function is to make up pressure inside the tank by letting air into the tank.

If this function is not performed correctly, the car may judder or stall due to difficulties in supplying the pump.

Seal if the car rolls over

The roll-over function prevents fuel emerging from the tank if the car rolls over or tilts to a great extent. During normal car operation (bends, acceleration, braking etc.), the fuel slops about and may emerge. The highly-sensitive roll-over valve prevents this happening.

DELIVERY MANIFOLD (RAIL)

The delivery manifold (rail) is fitted to the cylinder head on the intake side.

Its volume damps fuel pressure fluctuations due mainly to:

• operation of the pressure pump;
• injector opening.

A fuel pressure sensor is fitted in the middle of the delivery manifold. Hydraulic connections (high pressure) are via special steel pipes.