<div class="htmlview paragraph">In the search for fuel efficiency and emission control in modern gasoline powered automobile engine operation, the single largest problem is the knowledge of the state of the fuel involved. That is, when the fuel is totally liquid it can be handled in much the same way as a hydraulic system. In addition, when the fuel becomes a gas it will function in a manner similar to a pneumatic system. However, in a fuel system the actual state of the fuel depends on the composition of the fuel, the operating conditions, and the ambient conditions. To the authors' knowledge, the analytical model that describes the dynamic time-based performance of a fuel system has not been successfully formulated in the past due to the lack of an adequate time-based fuel state model.</div> <div class="htmlview paragraph">This paper will present a complete model of an engine fuel system along with a computer program that is capable of producing a computerized analysis of the dynamic performance for the system. The model will accept a constituent-type description of the fuel and a parametric designation for the operating and environmental conditions. Various component models will be utilized in constructing the fuel system. These components will be generic in nature to provide greater generalization. Finally the paper will present the simulation results for a practical fuel system using a realistic fuel.</div>