Aspects of the disclosure generally provide a heat engine system with a working fluid circuit and a method for starting a turbopump disposed in the working fluid circuit. The turbopump has a main pump and may be started and ramped-up using a starter pump arranged in parallel with the main pump of the turbopump. Once the turbopump reaches a self-sustaining speed of operation, a series of valves may be manipulated to deactivate the starter pump and direct additional working fluid to a power turbine for generating electrical power.