[ITSv40]

According to Haynes:

The evaporative emission control system is used to minimise the escape of evaporated fuel into the atmosphere. To do this, the fuel tank filler cap is sealed and a carbon - filled canister is used to collect and store petrol vapours generated in the tank. When the engine is running, the vapours are purged from the canister by means of a vacuum - driven, ECU-controlled solenoid purge valve. the vapours are then passed into the inlet tract to be burned by the engine during normal combustion. To protect the catalyst and to ensure that the engine runs correctly when idling, the purge valve only operates when the engine is running under load. As a safety measure, a roll-over valve is incorporated into the system which closes when the car tilts sideways by more than 45degrees. This prevents fuel leaking in the event of an accident. The carbon canister is located under the left-hand front wheel arch and the purge valve is located in the engine compartment, in front of the inlet manifold.

It appears to me that the OP needs to fit a new purge valve.