The purge valve for the Elantra RD series is under the hood between the brake booster and the left side wheel well. You access it by removing the air cleaner box, then it's relatively easy to replace.
I had the problem where it's really hard to fill your gas tank from the pump, the nozzle shuts off too easy. My evap system was clogged with charcoal pellets from the evap canister.
Four months on after I cleaned out my evap system. No more charcoal pellets coming out. I sealed up the canister with fiberglass mesh screen. My system seems to have fixed itself, I can fill my gas tank as fast as I want. Since there is no more charcoal coming out, I can fill my tank to the very top with no unintended consequences.
I was having a problem with the purge valve. Code P0441 Purge Valve incorrect flow. Difficulty starting when warm. I took it off and cleaned it. It was not sealing or actuating properly, and I could suck air through it. After cleaning it, it was sealing tight. I put it back on. Worked ok.
1000 miles later, I get a code again. This time P0441 along with P0445. P0445 is short circuit purge valve, which means the valve is now bad electrically. I found a replacement from the junkyard $2. All is well again.