A module for an on-board evaporative emission leak detection system that detects leakage from an evaporative emission space of an automotive vehicle fuel system, and corresponding method that calibrates a leak detection module pump to set a desired stroke of a moveable wall in the pump of such evaporative emission leak detection system. A pump disposed within interior space of the module has an inlet in communication with the interior space and an outlet that communicates through a flow passage with the evaporative emission space. A vent valve within the interior space is selectively operable to a first state that vents the flow passage to the interior space of the module, thereby venting the evaporative emission space to atmosphere, and to a second state that does not vent the flow passage to the interior space. An electromechanical actuator within the interior space operates the pump and the vent valve by respective magnetically responsive levers. An eccentric cam for calibrating a lever is disposed for abutment by an arm of the lever and turned to a position to secure a desired relationship between the pump and actuator.