MDE 16 End of Unit Quiz

Correct Answer: A. Regular calibration and testing of the level sensor
Explanation: Regular calibration and testing of the level sensor ensure that it provides accurate readings, thereby reducing the chances of false or spurious alarms.

Correct Answers:
A. Excessive fuel injection
B. Insufficient air supply

Explanation: Black smoke in marine diesel engines is commonly caused by excessive fuel injection or insufficient air supply, leading to incomplete combustion. High lubricating oil pressure and coolant leaks do not typically result in black smoke, while improper fuel timing could lead to different issues such as white smoke or engine knock, but not specifically black smoke.

Correct Answer: B) Build-up of carbon deposits on the valve
Explanation: Carbon deposits can accumulate on the valve, preventing it from sealing correctly and causing air to leak.

Correct Answer: A) It restricts oil flow; replace the oil filter

Explanation:
A blocked oil filter restricts oil flow, leading to low oil pressure. Replacing the oil filter will remove the blockage and restore proper oil flow and pressure.

Explanation:
When a cylinder air start valve is leaking, it poses a significant risk of air leakage into the cylinder, which can cause serious engine damage or even an explosion if left unchecked. The immediate response is to shut down the engine to prevent any further damage and isolate the affected cylinder to stop the air supply to it. Continuing normal operation (A) or increasing engine speed (B) would exacerbate the problem, and manually operating the valve (D) would not address the underlying issue safely.

Answer: B. Ensuring precision alignment during turbocharger installation
Explanation: Misalignment during the installation of the turbocharger can cause uneven stresses and vibrations. Ensuring precise alignment during installation ensures that the turbocharger operates smoothly without introducing vibration from misalignment.

Answer: B) By changing the fluid viscosity in the coupling

Explanation:
The transmitted torque in a fluid coupling can be varied primarily by changing the fluid viscosity within the coupling. The viscosity of the hydraulic fluid affects how much torque can be transmitted between the impeller and turbine. Higher viscosity increases the torque transmission capacity, while lower viscosity decreases it. Adjusting engine speed or the fluid temperature can influence the coupling's performance but does not directly vary the transmitted torque in the way changing fluid viscosity does. Adjusting the clearance between the impeller and turbine is not a standard method for varying torque transmission in fluid couplings.

Correct Answer: C) Clogged radiator or coolant passages

Explanation:
A clogged radiator or coolant passages can impede the flow of coolant, reducing the engine's ability to dissipate heat and leading to overheating.

Correct Answer: B) Debris lodged in the valve seat
Explanation: Debris lodged in the valve seat can obstruct the valve from closing fully, leading to a leak.

Answer: C. Ensuring regular cleaning of the turbine and compressor blades
Explanation: Fouling of the turbine and compressor blades can disrupt the smooth flow of air, leading to uneven pressure and vibration. Regular cleaning helps maintain proper airflow and minimizes vibration caused by blade fouling.

• Correct Answer: B) Clean the valve and seating area, and then reinstall

Explanation:
If debris is the issue, the appropriate action is to clean both the valve and the seating area to ensure a proper seal. Replacing the valve (A) may not be necessary if cleaning resolves the issue, and increasing air pressure (C) could cause more damage. Blocking off the air supply (D) might temporarily stop the leakage but is not a permanent fix and could lead to further complications.

Correct Answer:
A. Clean or replace the air filters

Explanation:
Insufficient air supply in marine diesel engines can lead to poor combustion, resulting in black smoke and reduced engine performance. Cleaning or replacing the air filters ensures that the engine receives adequate air for combustion. Increasing fuel injection pressure, reducing engine load, or adjusting fuel injection timing do not directly address the issue of insufficient air supply.