Question 66 3AE01 - Third Assistant Engineer

The Correct Answer is C. ### Why Option C is Correct: **C) A serious hazard of blood poisoning exists if the fuel spray penetrates the skin of the operator** This statement is correct because diesel fuel injection systems operate at extremely high pressures (often hundreds or thousands of psi). If the concentrated fuel spray from the nozzle penetrates the skin (known as "diesel injection injury" or "high-pressure injection injury"), the fuel is forced directly into the subcutaneous tissues. This constitutes a severe medical emergency. The chemical nature of the fuel, combined with the extreme pressure and physical trauma, leads to rapid tissue necrosis (death) and can cause systemic toxicity and infection (including septicemia or blood poisoning), often requiring immediate surgical intervention (amputation is sometimes necessary if not treated promptly). Therefore, ensuring the operator never exposes their skin to the spray is the most critical safety precaution. ### Why the Other Options are Incorrect: **A) The valve should normally begin to open at 1/2 the popping pressure** This is incorrect. Nozzle opening pressure is a specific, calibrated setting. The valve must remain tightly closed until the full specified popping pressure is reached to ensure proper fuel atomization and timing. Beginning to open at half the pressure would indicate a severely faulty or weak spring. **B) The needle valve spring should always be removed first before testing** This is incorrect. The needle valve spring is essential for setting the opening pressure and providing the force needed to snap the nozzle shut. Removing the spring would prevent the nozzle from building any pressure and would not allow for a proper functional test. **D) The needle valve should remain open after the nozzle pops open** This is incorrect. For proper operation, a diesel injection nozzle must open and close very rapidly (a sharp "pop") to correctly atomize the fuel and ensure the correct injection window. If the needle valve remains open after the initial pop, it is called "dribbling" or "weeping." This indicates a fault, such as excessive wear or insufficient spring tension, and leads to poor engine performance and excessive smoke.