Question 41 QMED03 - Oiler

The Correct Answer is C **Explanation for Option C (Jerk pump injection):** The Jerk pump injection system (also known as the inline pump injection system) perfectly matches the description: * **Individual pump for each cylinder:** A key characteristic of the jerk pump system is that it uses a high-pressure pump element (plunger and barrel) dedicated to pressurizing and metering the fuel for each individual cylinder. These pump elements are housed within a single inline pump unit. * **Spring-loaded differential spray needle valve:** This system utilizes a conventional, mechanically operated injector nozzle. This nozzle contains a spray needle (or pintle) held against its seat by a strong spring. The 'differential' aspect refers to how the pressurized fuel acts on the needle's differential area to lift it rapidly off its seat once the required opening pressure is reached, resulting in rapid, high-pressure injection and atomization. **Explanation for Incorrect Options:** **A) Common rail injection:** This system uses a single, high-pressure pump (or a few pumps) that continuously maintains extremely high pressure in a shared fuel rail (the "common rail"). The fuel is injected into the cylinders by electronically controlled injectors (solenoid or piezoelectric), not by individual mechanical pumps, and the injectors are typically electronically controlled, not solely spring-loaded mechanical valves. **B) Air injection:** This is an obsolete system where fuel is forced into the cylinder by highly compressed air, rather than solely by hydraulic pressure generated by a pump. It does not use the described mechanical jerk pump components or individual pumps for the hydraulic pressure required in modern high-speed diesels. **D) Distributor injection:** In this system (often associated with Stanadyne or Lucas/CAV pumps), a single high-pressure pump element is used to pressurize and meter the fuel. This single high-pressure charge is then directed, via a mechanical rotor (distributor), to the correct output line leading to the respective cylinder's injector. It does not use an *individual pump* for *each cylinder*.