Fuel Cap
WARNING: This page is about a different car, the 2002 Saturn LW200, 2002 Saturn L200, and 2002 Saturn L100. However, it is still accessible from the selected car via links, so may be relevant.
The fuel cap seals the inlet end of the fuel filler pipe and prevents the escape of fuel liquid and vapor. It is tethered to the fuel door on the vehicle body to prevent loss. The cap requires 1/4 turn (plus an additional 1/4 turn to activate at least three "clicks" of the ratcheting top feature) to engage the filler pipe neck during installation.
The cap also incorporates a spring-loaded, "free-spin" feature (about 150 degrees) noted during removal.
The cap is vented to the atmosphere in both positive and negative (vacuum) pressure modes to prevent build-up of excessive pressure in the system.
The cap is designed to vent at a positive pressure of about 2 psi. (56 in. H2O) and negative pressure (vacuum) of about 1 psi. (28 in. H2O).