Question 189Motor Plants - Assistant Engineer

The correct answer is D) the cylinders are not chilled by the expansion of the starting air. In a medium-speed marine propulsion engine equipped with direct admission air starting valves, the cylinders without air starting valves fire first because the lack of chilling from the expansion of the starting air allows these cylinders to reach the necessary temperature and pressure for combustion more quickly during the starting process. The other answer choices are incorrect because they do not directly address the reason for the specific firing order of the cylinders in this type of engine.