單項選擇題The amount of fuel injection into a diesel engine cylinder by a unit injector, is controlled by（）

A.the firing pressure in the cylinder
B.a metering helix inside the pump
C.varying the physical length of the plunger stroke
D.varying the clearance between the injector cam and the injector rocker arm


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1.單項選擇題Which of the following should always be checked prior to starting a diesel engine?（）

A.Air filters
B.Fuel oil strainers
C.Crank case oil level
D.Pyrometer readings

2.單項選擇題An after-cooler installed between the turbocharger and the cylinder air inlet （）

A.increases the density of the air
B.decrease the density of the air
C.increases the specific heat of the air
D.decreases the specific heat of the exhaust

3.單項選擇題Proper lubrication of the main bearings is more easily obtained in a single acting, four-stroke/cycle diesel engine than in a tow-stroke/cycle diesel engine because（）.

A.The direction of pressure on the journal in four-stroke engine is continuously
B.positive feed lubricators are installed on all bearings of four-stroke engine, whereas as a splash feed system is used on tow-stroke engine
C.four-stroke engines usually utilize a heavier grade of oil than tow-stroke engines
D.Low-stroke engines usually consume less lube oil than four-stroke engines

4.單項選擇題If the low level alarm of the diesel fuel day tank fails to function, you can expect trouble from（）

A.overheated injection pumps
B.water condensed in the cylinders
C.fuel dilution of the lube oil
D.air in the fuel system

5.單項選擇題Before starting a diesel engine, you should always（）

A.check the pyrometer readings
B.check the crankcase oil level
C.check the fuel oil strainers
D.clean the fuel system