Question 31 AEL01 - Assistant Engineer - Limited

The Correct Answer is D **Explanation for Option D (barrel):** In a typical mechanical fuel injection pump (like the jerk pump shown in illustration MO-0061), the component labeled "N" is the stationary outer cylinder or housing within which the plunger (the piston-like component) reciprocates. This component is crucial as it contains the high-pressure chamber, the inlet port, and the spill port. This stationary component is correctly identified as the **barrel** (or sleeve/barrel assembly) in which the plunger operates. **Why the other options are incorrect:** * **A) control rack:** The control rack is the geared bar that moves axially to rotate the plunger, thereby changing the effective stroke and the amount of fuel delivered. It is a separate external component that interacts with the plunger via a control sleeve or quadrant, not the main housing labeled "N." * **B) sleeve:** While the barrel is sometimes referred to as a sleeve, in the context of identifying distinct components within this specific pump design, the term "sleeve" often refers to the **control sleeve** (or quadrant) which is fitted around the plunger and driven by the control rack to rotate the plunger. The stationary housing "N" that contains the plunger is most accurately and commonly termed the barrel. (Note: Since "barrel" is a provided option, it is the superior choice over "sleeve" for component N.) * **C) plunger:** The plunger is the piston-like component that moves up and down (reciprocates) inside the barrel to compress the fuel. It is the moving part that creates the high pressure, not the stationary component labeled "N."