GM-GMC: fuel tank pressurizing, vent line, purge solenoid

Question
hello my fuel tank pressurizes everytime .my eng service light has 2 evap codes,I checked the vent line on the filler neck it is ok,but if blow air into the line pressure comes back out.I had thefuel pump replaced at 120,000km,the 2002chev Silverado now has290,000km I have to clear these code to pass emmissions test,is my fuel tank purge solenoid the problem?

Answer
http://www.youtube.com/watch?v=CkgrMasd57s < that is a video on how to test the pressure sensor on 2002 silverado.

I have not heard of a purge solenoid however there is a pressure sensor and that could definitely be the problem.

Let me know if this helps. If you have any other info let me know so I can possibly help further.