Abstract: A combined fuel supply and priming system for diesel engine is disclosed. The fuel supply portion of this system may be conventional and may include a fuel supply tank, a primary fuel filter, a fuel pump, a secondary fuel filter, and a plurality of injectors for injecting diesel fuel into combustion chambers of a diesel engine. A fuel line connects these parts so that diesel fuel flows through the parts in the order named. The fuel supply system may further include a return line leading from the injectors back to the fuel supply tank. The priming portion of the system includes a manually operated primer pump, which may be connected either in line with the other parts or via a bypass connection. When the primer pump is connected in line, it may be placed between the fuel pump and the secondary fuel filter. In line connection provides a single flow path for fuel used either for priming or for normal operation.