🔍 Key Concepts

• Basic diesel engine principle – how ignition happens without a conventional spark • Difference between diesel and gasoline engine ignition systems • Role of compression vs. external ignition devices (spark plugs, glow plugs)

💭 Think About

• In a running diesel engine, is the fuel ignited by an electrical spark or by conditions created inside the cylinder itself? • Which listed components are actually used on gasoline engines rather than diesel engines during normal operation? • What happens to air inside the cylinder just before fuel is injected, and how does that affect temperature?

✅ Before You Answer

• Identify which options are parts of a gasoline engine (not normally used to ignite fuel in a diesel cylinder). • Recall that a diesel engine relies on very high compression ratios—what effect does this have on the air temperature in the cylinder? • Consider which device (if any) is only used for starting in cold conditions, not for continuous ignition in normal running.