🔍 Key Concepts

• Relationship between compression pressure and sealing of the combustion chamber (piston rings, liner, valves) • Effect of injection timing on peak firing pressure versus compression pressure • How engine load affects all cylinders compared to a single cylinder

💭 Think About

• Ask which fault would reduce both compression pressure (before fuel injection) and firing pressure (after combustion) in ONE cylinder • Consider which options would affect ONLY the combustion event timing/strength but NOT the mechanical sealing of the cylinder • Think about what would happen to compression readings if you shut off fuel to that cylinder completely—what does that tell you about which factors influence compression?

✅ Before You Answer

• Identify which choice directly affects mechanical sealing of the cylinder (before fuel is injected) • Separate faults that would change timing of combustion from faults that change ability to hold pressure • Confirm that engine load would influence all cylinders similarly, not just one, unless there is a specific defect in that cylinder