A fuel injector for delivering fuel to an internal combustion engine. The fuel injector includes a fuel injector housing, a system for metering vaporized fuel to the internal combustion engine, the system positioned within the fuel injector housing, and a system for delivering an atomized stream of liquid fuel to an internal combustion engine, the system positioned within the fuel injector housing, wherein the fuel injector is operable to transition from metering vaporized fuel to delivering an atomized stream of liquid fuel to an internal combustion engine. The system for metering vaporized fuel includes at least one capillary flow passage, the at least one capillary flow passage having an inlet end and an outlet end; a heat source arranged along the at least one capillary flow passage, the heat source operable to heat the liquid fuel in the at least one capillary flow passage to a level sufficient to change from the liquid state to a vapor state and deliver a stream of vaporized fuel from the outlet end of the at least one capillary flow passage. The system for metering vaporized fuel further includes a valve for metering vaporized fuel located downstream to the outlet end of the at least one capillary flow passage. The fuel injector is effective in reducing cold-start and warm-up emissions of an internal combustion engine.