单项选择题
A.too light of a load
B.injection timing is too early
C.overloading of the engine
D.too low of a compression ratio
单项选择题 The knock occurring when a cold diesel engine is started and continues while running at low speed, but stops when the engine reaches normal operating speed and temperature, is（）.
单项选择题 Failure to open the diesel engine test cocks after a long period of shutdown, prior to starting may result in （）
单项选择题 Heat damage to fuel injection nozzles can be prevented by avoiding （）