Question 155Motor Plants - Assistant Engineer

The correct answer is B) exhaust valve spring. The exhaust valve spring is responsible for closing the exhaust valve in a diesel engine, allowing the engine to properly expel the exhaust gases after the combustion cycle. This component is a critical part of the engine's valve train and is labeled as "1" in the provided illustration MO-0122. The other answer choices are incorrect because: A) external thread is not a engine component, C) inlet valve spring controls the intake valve, and D) conical speed/surge prevention device is not a standard diesel engine component.