🔍 Key Concepts

• Jerk-type diesel fuel injection pump operation sequence (suction, pressurization, injection, cutoff, and pressure decay) • Function of a delivery check valve in maintaining or releasing pressure in the high‑pressure fuel line • Difference between cutting off injection at the nozzle vs. preventing reverse flow back into the pump barrel

💭 Think About

• When the plunger in a jerk pump stops or begins to move down, what happens to the pressure in the high‑pressure fuel line, and how does the delivery check valve affect this? • If the delivery check valve were removed, what two problems might occur in terms of fuel spray at the injector and fuel motion in the line and pump barrel? • Does the same component that prevents fuel from moving backward also influence how sharply fuel injection ends at the nozzle?

✅ Before You Answer

• Be clear on whether the nozzle needle valve or the delivery check valve primarily controls the end of injection and the quality of cutoff. • Confirm whether the delivery check valve’s design (spring‑loaded, one‑way) inherently prevents backflow from the high‑pressure line to the pump. • Think about which functions are primary design purposes and which are secondary side effects of the delivery check valve.