Question 17

The Correct Answer is B **Explanation for Option B (Unit injector type system):** The Unit Injector System (UIS) is characterized by having the high-pressure generation mechanism (the pump plunger) and the injector nozzle integrated into a single physical unit, which is typically mounted directly into the cylinder head. In this design, the fuel is pressurized to very high levels *within* the injector body itself, moments before injection. Because the high-pressure generation occurs right at the point of injection, there is no need for external high-pressure fuel lines running from a separate injection pump to the injector. The only fuel lines required are low-pressure lines to supply the fuel to the unit injector. Therefore, it exhibits a complete absence of high-pressure fuel lines. **Why the other options are incorrect:** * **A) In-line multi-plunger type system:** This system utilizes a dedicated injection pump (usually mounted externally) with separate plungers for each cylinder. Very high-pressure fuel lines are absolutely necessary to transport the pressurized fuel from the pump outlet to the remote injector nozzle located in the cylinder head. * **C) Rotary plunger type system:** Similar to the in-line system, the rotary (or distributor) pump is a separate component that pressurizes the fuel. High-pressure lines are required to distribute the pressurized fuel from the pump to the individual injectors in the cylinders. * **D) Common rail type system:** This system is defined by a central accumulator (the common rail) that constantly stores fuel at extremely high pressure (often exceeding 2,000 bar). High-pressure lines are mandatory to connect the high-pressure pump to the rail, and then additional high-pressure lines connect the rail to each individual injector.