🔍 Key Concepts

• Four-stroke diesel engine cycle and what happens just before combustion • Main functions of a fuel injection system (beyond metering and atomizing) • Relationship between injection timing and efficient combustion

💭 Think About

• In the engine cycle, when should fuel enter the cylinder relative to compression and top dead center (TDC)? • Which option describes something that must happen precisely every power stroke to ensure proper combustion? • Look at each choice and ask: Is this a direct, core job of the injection system, or a secondary effect of combustion and air motion design?

✅ Before You Answer

• Identify which choices describe air motion in the cylinder (turbulence/scavenging) rather than the injector’s main role • Ask which function, if done wrong, would most immediately cause misfiring or loss of power • Confirm which task is directly controlled by the fuel pump and injector cam/timing gear in a diesel engine