單項(xiàng)選擇題Under normal conditions, the main source of crankcase oil contamination is attributed to （）

A.metal particles loosened by wear
B.air when air cleaners are not used
C.condensation of water vapors
D.breakdown of the lubricating oil by dilution


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1.單項(xiàng)選擇題Valve cages are used on some large diesel engines to （）

A.reduce wear on the valve stem
B.permit the use of alloy valve seat materials
C.reduce heat transfer from the valve seat
D.facilitate valve removal for servicing

2.單項(xiàng)選擇題If the jacket water temperature rises rapidly above normal in a diesel engine, you should FIRST （）

A.place standby cooler in operation
B.reduce engine load
C.check thermostatic valve
D.clean sea water strainer

3.單項(xiàng)選擇題Which of the following conditions can cause excessive lube oil consumption in a diesel engine?（）

A.Low lube oil temperature
B.Dirty lube oil strainer
C.Low lube oil pressure
D.High lube oil temperature

4.單項(xiàng)選擇題In the common rail system, excessive pressure in the header may be caused by （）

A.improper adjustment of the bypass valve
B.a dribble in the fuel injection nozzle
C.insufficient leak-off through injection nozzle packing
D.a malfunctioning injection nozzle

5.單項(xiàng)選擇題Diesel engine valve springs function to （）

A.hold the valves open
B.keep the valves off their seats until the exhaust stroke is completed
C.close the valves
D.open inlet valves when the air injection cycle begins