If it clicks rapidly that is normally indication of faulty valve, putting another live replicates it being connected to the connector as it is constant live and you have 12V at the power connector, switched earth via ECU. Not sure on EEC but on the likes of Escos the ecu can rapidly pulse valve as well it it detects problem but not sure on your car. If his saying you can't use valve assuming his reputable specialist then must be right, I would ask someone who has FRST as I am sure other people do this.

Martin