The purge valve is energizes by the ECU when the engine is warm. The sig is an oscillating on/off frequency so as not to cause a large vac leak on the engine. By holding the valve in your hand ,you can feel the on/off oscillations.
When you do , pull the vac line of the valve on the outlet side and feel for suction at the valve port.

They have a tendency to stick and sometimes a slight rap gets them going again.
If no beat is felt , use at test lamp at the plug and you should see a clicking on/off lamp.
You may also check for vac. at the intake side of the valve just to verify eng vac to the valve.
I have hads luck with sticky Purge valve operation by squirting WD-40 in the hose between the valve and the charcoal canister and then rehooking up the line to pull the lube into the valve assem.
Also, I have seen purge valves that stick in the open position. This will cause an evasive internal vac leak noticed by rough idle
and other vac leak symptoms. This can be check by unplugging the electric connector and feel for suction at the outlet port. There should be none...