Abstract: An adjustable fuel delivery regulation assembly is provided which can be disposed within a direct oxidation fuel cell system, or the fuel reservoir or fuel tank that supplies such a system. One embodiment of the fuel delivery regulation assembly is a shutter assembly, which includes two correspondingly perforated components. The two components can be positioned relative to one another such that the apertures in each component are aligned in certain ways. In an open position, the apertures are substantially fully aligned to permit full fuel flow. In a closed position, the apertures are offset such that there is no opening; thereby fuel flow is restricted. Intermediate positions allow adjustments in the amount of fuel flow proportional to the size of the openings. In accordance with another embodiment of the invention, a set of rotatably mounted slotted rods is inserted into a housing through which fuel can flow through openings in the housing.