The purge valve will alaways have battery voltage The pcm pulses the ground when it is purging. The green cap is the service port to smoke the evap system.
You can also check the purge valve for a leak when the vehicle is running and purge valve comes on. When it is purging disconnect evap hose from the purge. You should feel a vacuum when disconnected. If you do it is purging.
While the hose is still disconnected, unplug the electrical connector to the purge valve. Check for vacuum at the solenoid There should be no vacuum at all. If there is replace the purge valve.
As for smoking and pinching off the vent hose yes the hose at the vent valve. Let smoke come out first just to verify there is no blockage and once it smokes pinch it off and check for any leaks.
If there is no check engine at this time then yes do a drive cycle to see if the evap monitor sets to complete without setting a code before you go through all that trouble.
Good luck and let us know what happens.
Sunday, May 21st, 2017 AT 7:20 PM