🔍 Key Concepts

• Types of fuel injection systems in diesel engines • How individual-cylinder pumps differ from systems using a common rail or distributor • Design and purpose of a spring-loaded differential spray needle valve

💭 Think About

• Which systems typically have one high‑pressure pump for every cylinder, and which use a shared high‑pressure source? • In which system is the injector nozzle itself controlled directly by the pressure generated in that cylinder’s own pump stroke? • How do air injection and common rail systems deliver fuel to the nozzle compared with mechanically timed pumps?

✅ Before You Answer

• Identify which option is known for separate, mechanically timed pumps for each cylinder • Confirm which system uses mechanical opening of the injector needle by fuel pressure overcoming a spring in a differential-area needle valve • Eliminate any systems that rely on shared high‑pressure fuel lines (common rail or distributor type) or compressed air to inject fuel