A method and system for an external combustion engine operable using at least two different fluids to provide pressure volume work to an engine. The engine is started by providing a compressed fluid at a sufficient pressure to move internal components of the engine that in turn rotate a shaft to generate power. At the same time the compressed fluid is provided to the engine, a liquid fluid is provided to a heater to be heated. The liquid fluid is heated to its boiling point and converted to gas form. Additional heat is provided to increase the pressure of this gas fluid. Once the pressure is increased to a sufficient level, the gas fluid is injected into the engine to generate power. The gas is exhausted from the engine, and is cooled and separated back into the two separate fluids. The initial compressed fluid is recompressed for later use.