Abstract: A fuel delivery system for an internal combustion engine is disclosed. The system includes primary and auxiliary heating means for vaporizing a liquid fuel, vapor storage means, carburetor means including metering venturi means for mixing the vaporized liquid fuel with atmospheric air to provide a combustible air/fuel mixture and means for controlling the delivery of vaporized fuel to the carburetor means. The carburetor means may be connected to a conventional internal combustion engine intake manifold for eventual delivery of the combustible mixture to the combustion chambers of the engine. The vaporized liquid fuel delivery means of the system includes a variable orifice vapor delivery nozzle for modulating the vaporized fuel content of the air/fuel ratio of the combustion mixture.The auxiliary heating means are operative to provide an initial supply of vapor to a vapor reservoir upon start-up of the internal combustion engine.