Is it possible to run an extra ground wire to the evaperator control?

Hi Joe, supplying s ground would only "trigger" the purge valve keeping it open. You need to figure out why the computer is not "triggering" the device. Evap systems are tricky to diagnose. Some scan tools will operate the solenoids with bi-directional controls to test the system, also shops have a "smoke machine" that alows inert gas to enter the evap system if there is a leak you see where the smoke leaks out. There is a company that independent auto repair shops get their information from, this same information is available inexpensively for people that work on their own cars.. The information is year make and model specific, covering repair procedures, torque specifications, fluid capacities and specifications, service bulletins, component locations, wiring diagrams ect.... Alldata is very easy to navigate http://bit.ly/AllData_Repair_Manuals_Online