Question 465Motor Plants - Assistant Engineer

The correct answer is D) excessive air leakage by rings and valves. Explanation: A four-stroke cycle diesel engine requires proper compression to ignite the fuel and start the engine. Excessive air leakage past the piston rings or through the valves would result in reduced compression, preventing the engine from starting at normal cranking speed even with normal fuel pressure and ambient temperature. The other options, such as glazed liners/pistons, high lube oil pressure, or excessive compression ratio, would not directly cause a failure to start in this scenario.