Question 443Motor Plants - Assistant Engineer

The correct answer is B) insufficient compression. A diesel engine requires sufficient compression in the cylinders to ignite the fuel. If the compression is too low, due to issues like worn piston rings, leaking valves, or other mechanical problems, the engine will fail to start when being cranked. The other options are not directly related to the failure to start due to compression issues. High cetane number (A) refers to the fuel's ignition quality, not the engine's compression. Low lube oil viscosity (C) or high lube oil pressure (D) may impact engine operation, but they do not directly cause a failure to start due to insufficient compression.