Question 419Motor Plants - Assistant Engineer

The correct answer is B) a special cleaning wire. The spray holes in diesel engine fuel valves should be cleaned using carbon solvent and a special cleaning wire. This is because the spray holes are very small and delicate, and using a wire that is specifically designed for this purpose is the best way to ensure that the holes are properly cleaned without damaging them. Using other materials like diesel fuel, a copper wire brush, or a wooden dowel could potentially damage the spray holes and cause issues with the engine's fuel system.