🔍 Key Concepts

• Fuel injector operation – how fuel pressure overcomes a spring to start injection • The difference between the plunger (which creates pressure) and the needle valve/nozzle valve (which actually opens the spray holes) • How the lower end of the injector near the spray tip is constructed in the illustration (parts 31–34 and part 36)

💭 Think About

• In the illustration, trace the path of fuel from where it is pressurized to where it leaves the nozzle holes. Which internal part must lift to uncover those holes? • Which part in the drawing is directly exposed to high-pressure fuel on its underside and opposed by a spring on its top side? • Is the plunger the part that seals the nozzle holes, or does it only create pressure that acts on another smaller moving part near the tip?

✅ Before You Answer

• Identify which labeled item is the moving valve element at the nozzle tip that seats against an orifice. • Confirm which part in the diagram is called the plunger and note that it mainly provides pumping action, not nozzle opening. • Compare the labels: does part 33 or part 36 clearly appear at the needle tip area, and which one seems to be the actual valve that lifts off its seat?