Question 231Motor Plants - Assistant Engineer

The correct answer is C) pressurize the lube oil system with the prelube pump. Before starting a diesel engine with an engine-driven lube oil pump, the operator should pressurize the lube oil system using the prelube pump. This ensures that the engine bearings and other critical components are adequately lubricated before the engine starts, preventing potential damage from dry starts. The other options are incorrect because: A) opening the bypass line would depressurize the system, B) cutting in the lube oil cooler is not necessary for starting the engine, and D) topping off the expansion tank does not directly pressurize the lube oil system.