In a constant displacement fuel system, where does the bypassed excess fuel go?

• A. To the fuel tank
• B. Back to the pump inlet
• C. Out to the atmosphere
• D. Into the engine exhaust

Answer: (B)

In a constant displacement fuel system, the pump moves a fixed amount of fuel with each stroke. When the engine doesn’t need all that fuel, the excess is diverted through a bypass relief path back to the pump inlet. Returning the fuel to the inlet keeps the pump dealing with a constant volume and maintains steady discharge pressure downstream, preventing pressure spikes and ensuring reliable metering. Fuel being dumped to the atmosphere or into the exhaust would waste fuel and create safety issues, and while some systems return excess to the tank, this specific design routes it back to the pump inlet to keep the loop closed and the pressure stable.