單項選擇題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（）.

A.caused by retarded injection timing
B.caused by a mechanical defect in one cylinder
C.caused by high fuel injection pressures
D.normal for these conditions


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1.單項選擇題Failure to open the diesel engine test cocks after a long period of shutdown, prior to starting may result in （）

A.an air bound fuel system
B.damage to cylinder heads and pistons
C.excessive fuel injection
D.excessive air valve lift

2.單項選擇題Heat damage to fuel injection nozzles can be prevented by avoiding （）

A.excessive fuel oil temperature
B.long periods of engine overload
C.metallic contact between nozzles and cylinder heads
D.hard carbon deposit and varnish on the nozzles

3.單項選擇題Critical speed in diesel engines occurs when engine torque pulsations become （）

A.opposed to the crankshaft rocking couple
B.resonant with the crankshaft natural frequency
C.critical fore and aft crankshaft vibrations
D.horizontal whipping motions of the crankshaft

4.單項選擇題Air receivers installed in starting air systems are to be （）.

A.cylindrical in shape with service connections located at the top and bottom
B.opened and made available for inspection during biannual inspections provided
C.with automatic drain traps for the removal of moisture
D.so installed as to make the drain connections effective under extreme conditions of trim

5.單項選擇題Which of the conditions listed may occur in an operating diesel engine if air pockets form within the cylinder head circulating water passages? （）

A.Hydraulic stress and distortion will develop
B.Hot spots will develop
C.Fuel oil viscosity will increased
D.An increase in trapped deposits of scale and dirt