What are the rated flow and pressure for the fuel service pump at low and high speeds?

• A. 20 GPM at 100 PSIG; 40 GPM at 100 PSIG
• B. 36 GPM at 105 PSIG; 72 GPM at 105 PSIG
• C. 50 GPM at 90 PSIG; 100 GPM at 95 PSIG
• D. 30 GPM at 110 PSIG; 60 GPM at 110 PSIG

Answer: (B)

The fuel service pump is designed to deliver a steady discharge pressure to the fuel-control system, while its flow capacity changes with engine speed. The regulator keeps the system pressure around a fixed value (about 105 psi) so metering remains accurate, regardless of speed. As a result, at the low-speed setting the pump delivers roughly 36 GPM at 105 PSIG, and at the high-speed setting it delivers about 72 GPM at 105 PSIG. The higher speed simply moves more fuel, but the pressure is held constant by the regulation, ensuring consistent fuel metering across operating conditions.