got this from another post on the forum. has the part number and it is pretty easy to replace. i did this on a buddies truck and it took less than an hour.
Here is what is it called and how to fix it:
AC DELCO 214-2149 [CANISTER PURGE SOLENOID VALVE]
Features:
Brand new AC DELCO component with correct connector
Replaces dealer part numbers: 25932571, 214-2149
-It started off as 'Tighten Gas Cap" on the DIC, As the solenoid valve was stuck open and would vent the tank so the computer thought the gas cap was loose. I got the solenoid unstuck but later it failed in the close position and would not vent when filling the tank. I too tried everything including turning the nozzle completely upside down but the nozzle would just click off. The day after I replaced it I was able to fill the tank as fast as the pump would go and the engine light went out a day or so later, Have not had the problem ever since.
****UPDATE****
-Problem seems to be solved, I replaced the evap solenoid the day before yesterday and now I can fill the tank as fast as the pump will go. It only cost me $28, The engine light has not shut off yet but that should resolve itself in a few days after I drive it around a bit.
-It connects to the charcoal canister under the rear by the gas tank, A lot of people refer to it as the evap valve or solenoid.
-You have to crawl under but its just above and infront of the rear axel.
-A screw driver to pry up on the tab in the middle of the bracket and the same with tabs on the hose to release it. Then slide the new part back in the bracket and bend the tab back to hold it and make the connections.
-About 15 minutes of your time and no gas leaking, Also easier to get to if you drop the spare tire.
