A fuel vapor storage canister in an evaporative emission control system for a motor vehicle typically includes a mass of carbon granules in a carbon bed chamber of the canister which adsorb fuel vapor conducted to the canister from a fuel tank of the motor vehicle through a vapor transfer conduit. Fuel vapor is extracted from the carbon bed chamber through a vapor purge duct. Commonly, a liquid trap on the vapor storage canister captures liquid fuel entrained with the fuel vapor in the vapor transfer conduit to prevent contamination of the carbon granules. Liquid traps on some vapor storage canisters are passively purged, i.e., captured liquid fuel either evaporates from the trap or drains by gravity back to the fuel tank. Liquid traps on vapor storage canisters described in U.S. Pat. Nos. 4,714,485 and 4,853,009, issued Dec. 22, 1987 and Aug. 1, 1989, respectively, and assigned to the assignee of this invention, are actively purged, i.e., captured liquid fuel is induced by a pressure gradient between the liquid trap and the purge duct to flow from the liquid trap into the purge duct through a metering orifice submerged in liquid fuel in the liquid trap. A fuel vapor storage canister according to this invention is a novel alternative to the fuel vapor storage canisters described in the aforesaid U.S. Pat. Nos. 4,714,485 and 4,853,009.