What is the role of a governor on a fire pump engine?

• A. To regulate the electrical supply to the pump.
• B. To vent the discharge line.
• C. To adjust nozzle size.
• D. To maintain the desired discharge pressure by adjusting engine speed in response to system demand.

Answer: (D)

The governor's job on a fire pump engine is to keep the discharge pressure at the set point by adjusting the engine speed as demand changes. It senses the pressure in the discharge system and modulates fuel delivery to the engine, which changes pump speed and flow. When firefighters open more outlets and demand increases, the governor increases engine speed to raise the pump output and restore the target pressure. When demand drops, it lowers engine speed to prevent over-pressurization and wasteful fuel use. It isn’t responsible for electrical power, venting the discharge line, or changing nozzle size—those functions are handled by other parts of the system or by operator action, while the governor continuously tunes engine speed to match the hydraulic demand.