What are the two categories of engine-driven fuel pumps?

What are the two categories of engine-driven fuel pumps?

• A. Nonconstant displacement and nonpositive displacement
• B. Constant displacement and positive displacement
• C. Variable displacement and fixed displacement
• D. Piston-type and vane-type

Answer: (C)

Engine-driven fuel pumps are categorized by how their displacement responds to engine demand: fixed (constant) displacement versus variable displacement. A fixed-displacement pump delivers about the same amount of fuel per crankshaft revolution regardless of engine speed, so fuel flow is predictable but may require a regulator to maintain appropriate pressure. A variable-displacement pump, on the other hand, changes the volume it moves per cycle in response to engine needs, helping maintain a steadier fuel pressure as RPM and demand change. The combination of variable displacement and fixed displacement best captures the two fundamental ways these pumps regulate output. Other pairings mix pump construction (like piston-type vs vane-type) or use nonstandard terms that don’t describe the main method of controlling displacement.

Engine-driven fuel pumps are categorized by how their displacement responds to engine demand: fixed (constant) displacement versus variable displacement. A fixed-displacement pump delivers about the same amount of fuel per crankshaft revolution regardless of engine speed, so fuel flow is predictable but may require a regulator to maintain appropriate pressure. A variable-displacement pump, on the other hand, changes the volume it moves per cycle in response to engine needs, helping maintain a steadier fuel pressure as RPM and demand change. The combination of variable displacement and fixed displacement best captures the two fundamental ways these pumps regulate output. Other pairings mix pump construction (like piston-type vs vane-type) or use nonstandard terms that don’t describe the main method of controlling displacement.