Im in the midst of trying to figure out whats causing my 0440 evap code. Vehicle is a 1997 volvo 850 NA. When the car is warm I can put my hand on the purge valve and it is non stop clicking like really fast. Also when I pull the hose off of it on the canister side I cant feel any vacuum ( no I dont have a vacuum guage to check it). When I pull the hose off on the manifold side I can feel vacuum but it is not strong (vehicle running). All hoses have been replace and checked all the way back past the one way valve rite above the fuel filter. Where it goes out of site up to the top of the fuel tank Im not sure but never can smell any fuel of any kind especially at fill ups. What Im asking is this how the purge valve should function with the rapid clicking?