🔍 Key Concepts

• Operation of a mechanical fuel injection pump in a diesel engine • Role and purpose of the delivery check valve in maintaining line pressure • Difference between mechanical movement and fuel (hydraulic) pressure in opening valves

💭 Think About

• Trace the path of the fuel: how does fuel get from the pump barrel to the injector, and what actually forces it past the delivery check valve? • Ask yourself: does the check valve follow a cam/push rod directly, or does it respond to something happening in the fuel passage? • Consider how the valve behaves when pressure drops after injection—what closes it again, and what does that tell you about what opened it?

✅ Before You Answer

• Identify whether the delivery check valve is directly contacted by any mechanical part (cam, tappet, push rod). • Confirm that a check valve is usually a one-way valve that responds to a difference in pressure rather than a direct mechanical push. • Verify what component (if any) uses a spring in this system and whether that spring’s primary job is to open or to close the valve.