What happens to excess fuel not required by a constant displacement pump?

• A. A relief valve bypasses excess back to the pump inlet
• B. It vaporizes
• C. It is dumped overboard
• D. It stores in a separate tank

Answer: (A)

Constant-displacement pumps move a fixed amount of fuel with each cycle, so when more fuel is delivered than the system needs, the excess is routed back to the pump inlet through a relief valve. This keeps the system pressure within the desired range and prevents overpressure, while maintaining a steady supply to the metering device. Vaporizing, dumping overboard, or storing excess in a separate tank aren’t how this setup manages surplus fuel, as they either waste fuel or require extra components. Returning the surplus to the inlet provides continuous circulation and proper pressure regulation.