Fiesta Steve

Help required please. Purge valve (EVAP) I have a problem with my cars idle, have tracked it down (hopefully) to this valve. I have measured the resistance across the valve terminals at 31.5 ohm, what voltage should there be across the supply connector, I have measured 1.9v across them. Have tried a replacement valve with no joy, engine will not idle. I have since disconnected the 2 pipes from the valve & joined together , the car runs perfectly. I have no engine management light on.