🔍 Key Concepts

• Helical plunger fuel injection pump construction and parts (plunger, barrel, helix, ports) • How rotating vs. stroking the plunger affects spill ports and fuel quantity • Difference between pressure in the line and timing/quantity control inside the pump

💭 Think About

• Which component physically changes the alignment between the helix and the spill ports to start/stop fuel delivery? • Does changing discharge or return pressure actually change the amount of fuel per stroke in a positive-displacement pump? Why or why not? • In a helical plunger design, what motion is used to increase or decrease the effective pumping stroke?

✅ Before You Answer

• Identify which part has the helical groove/helix machined into it • Confirm which movement (rotation vs. up‑and‑down motion) is used by the fuel control rack or governor linkage • Verify that line pressure changes alone do not alter the fixed displacement of a plunger-type pump