單項(xiàng)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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單項(xiàng)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

單項(xiàng)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