🔍 Key Concepts

• How a diesel engine actually ignites fuel (compression ignition) • What happens to cylinder temperature and pressure when cranking speed is low • The relationship between cranking speed, fuel injection, and combustion

💭 Think About

• Ask yourself: In a diesel, what is the main thing needed inside the cylinder to ignite the fuel if there are no spark plugs? • Think about how slower cranking affects the air being compressed in the cylinder—does it get hotter, cooler, or stay the same? • Which of the choices directly depends on how much the air is heated during compression?

✅ Before You Answer

• Recall that a diesel relies on high compression temperature rather than a spark for ignition • Consider whether slower cranking will raise or lower the final compression temperature in the cylinder • Eliminate options that are more about fuel timing/exhaust effects rather than what is needed to start the engine initially