Question 22 DDE04 - Designated Duty Engineer - 1000-4000 HP

The Correct Answer is C ### Explanation of Why Option C (Unit Injector Type System) is Correct The **Unit Injector (UI)** system is characterized by combining the high-pressure fuel pump and the injector nozzle into a single unit, which is typically mounted directly in the cylinder head. Because the high pressure (required for atomization and injection) is generated *within* the unit itself, right at the point of injection, there is no need for external high-pressure fuel lines running from a central pump to the individual injectors. The system only requires low-pressure lines to deliver fuel to the units for supply and cooling. Therefore, it has a complete absence of high-pressure fuel lines. ### Explanation of Why Other Options Are Incorrect **A) Rotary plunger type system (Distributor pump system):** This system uses a central rotary pump to pressurize the fuel. The high-pressure fuel must then be delivered through individual **high-pressure fuel lines** to each nozzle in the cylinders. **B) In-line multi-plunger type system:** This older system uses an in-line pump with multiple plungers (one per cylinder). The fuel is pressurized by the pump and then delivered through rigid, **high-pressure fuel lines** to the injectors mounted on the engine. **D) Common rail type system (CRDI):** This system is defined by its use of a single, central high-pressure pump (or pumps) that continuously maintains extremely high pressure (25,000 psi or more) in a central accumulator, or "common rail." **High-pressure fuel lines** are essential to connect the pump to the rail and to connect the rail to each individual injector.