Question 50 OSE01 - Chief Engineer - OSV

The Correct Answer is C **Why Option C is Correct:** The description states that the pop-test results are otherwise acceptable: 1. **No leakage prior to popping pressure:** Indicates the needle valve and seat (Option D) are sealing correctly. 2. **Pressure holds just below popping pressure:** Confirms proper seal and spring tension (Option A). 3. **Popping pressure is within specification:** Confirms the tension set by the spring (Option A) is correct. The sole observed fault is a **distorted spray pattern**. The spray pattern is exclusively determined by the condition and cleanliness of the small holes (orifices) in the injector nozzle tip. If these orifices are partially blocked by carbon deposits or fuel residue, or if they are eroded, the fuel jet will be misdirected or unevenly distributed, leading to a distorted spray pattern. Therefore, the orifices must be cleaned (reconditioned) or the entire nozzle tip replaced. **Why the Other Options Are Incorrect:** * **A) The injector spring compression must be readjusted or a broken spring replaced:** This action is performed to correct issues with the **popping pressure**. Since the actual popping pressure is stated to be "within specification," the spring compression is correct, and the spring is functioning properly. * **B) The injector spindle and nozzle holder bore must be reconditioned or replaced:** Issues with these components usually relate to alignment, binding, or leakage in the internal hydraulic circuit. These components are not the direct cause of the spray pattern distortion observed at the moment of injection. * **D) The injector needle valve and seat must be reconditioned or replaced:** The condition of the needle valve and seat determines the **sealing ability** and whether the pressure holds prior to injection. The test specified "no leakage prior to reaching the popping pressure" and "the pressure holds at just below the popping pressure," confirming that the needle valve and seat are sealing correctly. If the seat were defective, the spray pattern might be distorted, but more significantly, the pressure would leak away rapidly, and the pop pressure would be difficult or impossible to achieve.