What effect does adjusting the spring force of a regulator have on fuel oil pressure?

Adjusting the spring force of a regulator directly affects the minimum pressure setting for the fuel oil system. The spring in a regulator is responsible for maintaining a specific pressure by pushing against the flow of fuel oil. When you increase the spring force, you raise the minimum pressure threshold that the regulator will maintain, meaning that the pressure will not drop below this adjusted level during normal operation. Conversely, if the spring force is decreased, the minimum pressure will be lower, allowing for greater variability in operating conditions. Therefore, the correct answer emphasizes how the spring function is critical for regulating and controlling the baseline pressure in the fuel oil system.