It’s a multi step process to cure…
1st: Replace charcoal canister that likes to break its membrane and let pellets into the fuel system. YOU WANT to find it intact.
2nd: Replace vapor purge valve assembly under truck. If this stops the clickity clack of the filler nozzle, you lucked out.
If you have pellets falling out of the carbon canister or the purge valve assemb doesn’t fix it, there’s more steps. The two parts above are known to fail at 10+ years. Replacing them is a must regardless of outcome.
Wrong order, parts cannon method. And we should use the correct terminology to minimize confusion.
First test the VENT (not purge; that's on the engine) valve that is under the backend of the truck. It should be open / vent with the key off / engine off while fueling. Adding fuel to the tank pushes fumes from the tank into the canister where the bad stuff is stored in the charcoal, and "clean" air is pushed out the vent valve. If that path is blocked in any way, it'll need to be cleared.
If the vent valve is working properly and the vent filter isn't plugged, open up the connections to the canister. If, when you pull the connections off the canister, charcoal pellets fall out of the canister or the lines, it's time for a new canister and having the lines blown out.
If you think you want more detail and a video or two to look at, let us know.
