Question 31 OSE02 - Assistant Engineer - OSV

The Correct Answer is C **Why Option C is Correct:** The problem described is a **distorted spray pattern**. The spray pattern is exclusively determined by the condition of the small holes (orifices) in the nozzle tip. If these orifices are clogged, partially blocked, damaged, or suffering from carbon build-up (which is common), the fuel stream exiting the nozzle will be uneven or improperly directed, resulting in a distorted spray pattern. Since the popping pressure and leakage tests (pre-pop leakage and pressure hold) passed successfully, the mechanical operation of the needle valve and the spring tension are confirmed to be within specification. Therefore, the maintenance needed is either cleaning the nozzle tip orifices (reconditioning) or replacing the tip if cleaning is insufficient or the damage is severe. **Why the Other Options are Incorrect:** * **A) The injector spring compression must be readjusted or a broken spring replaced.** This adjustment (or replacement) governs the **popping pressure**. Since the popping pressure was observed to be "within specification," the spring compression is correct, and no adjustment is necessary. * **B) The injector needle valve and seat must be reconditioned or replaced.** The condition of the needle valve and seat governs the sealing properties and the **pressure hold/leakage** characteristics. Since the observation noted "no leakage prior to reaching the popping pressure" and "the pressure holds at just below the popping pressure," the sealing (which is dependent on the needle valve and seat) is confirmed to be adequate. * **D) The injector spindle and nozzle holder bore must be reconditioned or replaced.** Wear between the spindle (needle valve guide) and the nozzle holder bore primarily affects the guidance of the needle valve and can lead to excessive blow-by (fuel leakage past the needle) or poor seating, which would manifest as poor pressure hold or leakage issues. Since the leakage characteristics were good, this component is unlikely to be the source of the spray distortion.