2002 Ford Explorer XLS 4.0L with code P1440

Question

Replaced purge valve next to charcoal EVAP canister cleared codes but codes P1440 01/01 reappears

Is there any way to test to check if the valve works?
Took a 400 km drive on the highway and noticed when arrived at destination gas gauge when first slowed down to city speed (50 km)
Displayed on red line then gauge few km at city speed s readjusted to over 1/8 full Is this normal?