MDE 14 Q3

Correct Answer: A. Check for leaks in the starting air system.

Explanation: After confirming that the air start lever is in the correct position, the next logical step is to check for leaks in the starting air system. Leaks can cause a drop in pressure, preventing sufficient air from reaching the cylinders to start the engine. This is a critical issue to address before considering other potential problems.

Correct Answer: B. Check if the main starting air receiver is pressurized.

Explanation: If the engine fails to start, the first thing to check is whether the main starting air receiver has enough pressure to deliver the required air for starting. Without sufficient pressure, the starting system won't function correctly, and the engine will not start. This is a fundamental step before checking more complex components like timing or fuel injectors.

Correct Answer: A) Pressure relief valve
Explanation: The pressure relief valve is a critical safety device in the air start system to prevent over-pressurization, which could lead to system failure or damage.

Correct Answer: A) Ensure that the engine cannot be started unless the turning gear is disengaged
Explanation: The interlock system prevents the engine from starting while the turning gear is engaged, which could otherwise lead to severe mechanical damage.

Correct Answer: C. Closed starting air supply valve.

Explanation: If no air is being delivered to the cylinders, one of the most likely causes is that the starting air supply valve is closed. This valve must be open to allow pressurized air to flow into the cylinders during the start sequence. Other issues like a faulty fuel pump or exhaust valve problems would not directly cause a lack of air delivery.

Correct Answer: A) To prevent backflow of air into the receiver
Explanation: The non-return valve ensures that compressed air does not flow back into the air receiver, which is crucial for maintaining system safety and efficiency.

Correct Answer: A. Air start valve stuck in the open position.

Explanation: If the air start valve is stuck in the open position, it can prevent the correct buildup and release of pressure needed to start the engine. This issue directly affects the air starting system and can lead to a failure to start. Other options like incorrect fuel injection timing or low engine coolant level, while important, do not directly impact the air starting process.

Correct Answer: B. Starting air valve condition.

Explanation: Air leakage during the start sequence often indicates a problem with the starting air valve, such as improper seating or wear. The condition of the starting air valve should be inspected to ensure it is functioning correctly and sealing properly to prevent leaks.

Correct Answer: A) Safety valve
Explanation: The safety valve releases excess air to the atmosphere when the pressure in the air start system exceeds a set limit, protecting the system from potential damage.