🔍 Key Concepts

• Construction and operation of a fuel injection jerk pump (barrel and plunger fit) • Importance of precise clearances between barrel and plunger for high-pressure fuel injection • Manufacturer and class/USCG guidance on replacing matched precision parts in fuel injection equipment

💭 Think About

• Think about how high the pressure is in a jerk pump and how small the clearances must be between moving parts for it to work properly. • Consider whether the barrel and plunger are manufactured and lapped together as a matched set, or if they are interchangeable parts. • Ask yourself what could happen to injection timing, pressure, and leakage if only one of two closely fitted parts is replaced.

✅ Before You Answer

• Verify whether the barrel and plunger are lapped/matched together during manufacture. • Consider if replacing only one component would affect sealing and fuel leakage at high pressure. • Think about standard maintenance practice for precision injection pump elements in marine diesel engines.