Fuel system

Fuel system

Fuel vapour cut-off solenoid (Siemens EC1)

The function of this valve is to control the quantity of fuel taken up by the active carbon filter and directed to the intake manifold (via the injection-ignition control unit).

The valve is closed when de-activated to prevent fuel vapours enriching the mixture excessively.

The injection-ignition control unit controls operation as follows:

• during start-up, the solenoid remains closed to prevent fuel vapour from enriching the mixture excessively. This condition persists until the coolant temperature reaches a pre-established threshold.
• with engine warm, the ECU sends the solenoid a square wave signal, which modulates opening in accordance with the signal empty/full pattern.

In this way, the ECU controls the quantity of fuel vapour sent to the intake to prevent significant changes in mixture concentration.

Under the service conditions listed below:

• throttle in idle position
• speed less than 1500 rpm
• intake manifold pressure less than a limit setting computed by the ECU according to rpm level

solenoid activation is inhibited to maintain the unit closed in order to improve engine operation.

Longitudinal section through fuel vapour cut-off valve

1. Valve core.
2. Reaction spring.
3. Magnetic winding.
4. Pipe connected to air intake manifold
5. Pipe connected to active carbon filter.

Wiring connector

The numbers in boxes indicate the corresponding control unit pins

Recovery

Mixture self-adaption is inhibited.

Mixture concentration test is inhibited.

Lambda probe test is inhibited.