Which component pressurizes fuel to the injection pressure in an older diesel system?

• A. High-pressure fuel rail
• B. Injection pump
• C. Lift pump
• D. Fuel filter

Answer: (B)

In an older diesel engine, the component that creates the high-pressure fuel needed for injection is the injection pump. Driven by the engine, it uses cam-driven plungers or similar mechanisms to compress fuel to the exact injection pressure and deliver it to the injectors at the right time. The timing and amount of fuel are controlled by the pump’s design and its synchronized operation with the engine, so it directly sets how much fuel enters the cylinder and when. The lift pump simply pulls fuel from the tank and feeds the injection pump at relatively low pressure; it doesn’t generate the high pressure required for injection. The fuel filter’s job is to remove contaminants, not pressurize fuel. The high-pressure rail is a feature of modern systems (like common-rail) and isn’t what creates the injection pressure in these older setups.