Abstract: A fuel delivery system for an internal combustion engine, including a vaporizing chamber for combining liquid fuel and air to produce a vaporized fuel and air mixture, a vapor expander which communicates with the chamber for expanding and further vaporizing the mixture, and a metering device which communicates with the expander and with the engine for supplying engine vacuum to the system and controlling the amount of the mixture which is supplied to the engine. The vaporizing chamber includes a reservoir for storing a quantity of liquid fuel, an air inlet, a jet which sprays liquid fuel into the chamber, and a reservoir heater which heats the liquid fuel in the reservoir. The vapor expander includes a tubular passage communicating between the chamber and the metering device and a heating conduit coiled around the tubular passage to carry heated engine coolant and transfer heat to the mixture.