What is the function of a governor in an air compressor or diesel engine?

• A. To lubricate bearings
• B. To control system pressure or engine speed by adjusting fuel/air supply to maintain a set point
• C. To monitor exhaust emissions
• D. To cool the engine

Answer: (B)

A governor regulates the output by maintaining a target level of either engine speed or system pressure through automatic adjustment of the fuel/air supply. In a diesel engine, it senses engine speed and increases or decreases fuel delivery to keep RPM at the set point, preventing overspeed or stalls as load changes. In an air compressor, it monitors the system pressure and adjusts fuel (and thus firing rate) to hold the pressure at the desired level, starting or stopping the compressor as needed to stay within bounds. The other options describe lubrication, emissions monitoring, or cooling—functions outside the governor’s control.