A fuel preconditioning system for use with a pulse detonation combustor (PDC) makes use of a heat source to pyrolyze fuel prior to injecting it into the PDC for detonation. The fuel is decomposed into a more detonable form by pyrolysis in a conditioner that applies heat to the fuel in the absence of oxidizer. The heat may be provided by a hot section of the engine, including the walls of the PDC itself. The conditioned fuel is fed to the PDC and detonated.