Hyundai Elantra: Emission Control System > Evaporative Emission Control System > Fuel Filler
Cap > Description and Operation
Description
A ratchet tightening device on the threaded fuel filler cap reduces the
chances of incorrect installation, which seals the fuel filler. After the gasket
on the fuel filler cap and the filler neck flange contact each other, the ratchet
produces a loud clicking noise indicating the seal has been set.