Question 248Motor Plants - Assistant Engineer

The correct answer is D) the ignition of unburned fuel and air in the crankcase. Crankcase explosions in propulsion diesel engines are typically caused by the ignition of unburned fuel and air that accumulates in the crankcase. This can happen due to issues like faulty fuel injectors, incorrect fuel-air mixture, or malfunctioning crankcase ventilation systems. The ignition of this unburned fuel-air mixture inside the crankcase can lead to a sudden pressure increase and result in a crankcase explosion. The other answer choices are incorrect because they do not directly lead to the ignition of unburned fuel and air in the crankcase, which is the primary cause of crankcase explosions in diesel engines.