🔍 Key Concepts

• Fuel oil service pump discharge and suction sides in a closed loop system • Purpose of a relief valve on positive displacement pumps (protecting the pump from overpressure) • Where excess fuel is normally routed so it can be safely reused without introducing air or overheating

💭 Think About

• On a positive displacement fuel service pump, what happens if the discharge line is blocked and there is no place for the liquid to go? Where must the relief valve send it? • Which destination would allow the fuel to be quickly recirculated without creating a large pressure drop, introducing air, or sending it too far away in the system? • Look at each choice: which one returns fuel to a place that the pump can handle easily and continuously if the relief is lifting for some time?

✅ Before You Answer

• Verify which side of the pump (discharge vs suction side) is normally used as the return point for a built-on relief valve in many positive displacement pumps. • Eliminate any choice that would send high-pressure relief flow to a location not designed for continuous recirculation of hot fuel. • Check which option best maintains a stable supply to the engine and avoids sudden temperature or level changes in more distant tanks or heaters.