Question 34

The Correct Answer is A. **Explanation for A (Worn blower rotor shaft seals):** The engine described is a two-stroke cycle diesel engine utilizing a Roots-type blower for scavenging and charging air. These blowers often require lubrication (usually from the main engine lube oil system or a dedicated system). If the blower rotor shaft seals wear out, the engine lubricating oil (lube oil) will leak past these seals and be carried directly into the scavenging air stream. This oil is then pushed into the cylinder, where it burns along with the fuel during combustion. The excessive burning of lube oil results in increased lube oil consumption and the emission of bluish-tinged smoke (the characteristic color of burning oil) from the stack. **Why the other options are incorrect:** * **B) Restricted blower air intake filter:** A restricted air filter limits the amount of combustion air entering the cylinder. This would lead to incomplete combustion of the fuel (rich mixture), resulting in black or grayish smoke, loss of power, and potentially increased fuel consumption, but it would not directly cause excessive lube oil consumption and blue smoke. * **C) Leaking fuel injector needle valve:** A leaking or "dripping" fuel injector causes poor atomization and incomplete combustion of the *fuel*. This results in black or gray smoke, increased fuel consumption, high exhaust temperatures, and potential cylinder washdown, but it does not introduce excess lube oil into the combustion chamber to cause excessive lube oil consumption and blue smoke. * **D) Restricted scavenging air intake ports:** Restricted ports (often due to carbon buildup or mechanical damage) limit the air flow necessary to clear the exhaust gases (scavenging) and provide fresh air for the next combustion cycle. Similar to a restricted air filter (B), this leads to a lack of air and incomplete combustion, typically producing black or gray smoke, not the blue smoke characteristic of burning lube oil.