An experimental study was conducted to study fuel injection characteristics through plain orifice injectors when the fuel was heated to the temperature higher than its boiling point. Three injectors with different orifice diameters were used to measure the flow coefficient (${alpha}$) for the injection pressure ranges of 3, 5, and 10 bar and the fuel temperature ranges between 50 and $270^{circ}C$. The study showed that ${alpha}$ decreases gradually with the fuel temperature below $180^{circ}C$ while it drops abruptly when the temperature goes beyond $187^{circ}C$, the boiling temperature of the fuel. The slope of ${alpha}$ bifurcated at the boiling temperature for different injection pressures, and ${alpha}$ decreased faster for the lower injection pressure due to the more active boiling in the injector. In addition, the larger orifice diameter had the higher ${alpha}$ value, and ${alpha}$ jumped at moderate temperature ranges when the injection pressure was low, implying the turbulent-laminar transition phenomena. The measured ${alpha}$ was plotted against the cavitation number($K_c$), and the characteristics were independent of the applied pressure for small injectors when the fuel was evaporated before it was injected.