Which of the following problems can cause fluctuating pressures in the closed cooling system of a main propulsion diesel engine?（）

单项选择题If fuel injection to a four-stroke cycle diesel engine begins earlier than designed, ignition may be delayed because the （）.

A.cylinder compression pressure may not be high enough
B.cylinder compression temperature may be too high
C.fuel oil injection pressure may not be high enough
D.scavenge and purge process is incomplete

单项选择题Any increase in the exhaust back pressure of a four-stroke cycle diesel engine will （）.

A.reduce engine horsepower output
B.aid in silencing the exhaust noise
C.increase the mean effective pressure
D.contribute to effective cylinder scavenging

单项选择题High exhaust temperature and black smoke exhausting from an auxiliary diesel engine can be caused by （）.

A.engine overload
B.low combustion temperature
C.plugged fuel nozzle holes
D.excessive compression pressure

单项选择题On most diesel engines, the governor controls the output speed by （）.

A.controlling the amount of fuel injected into the cylinders
B.varying the speed of the turbocharger
C.adjusting the compression ratio
D.changing the timing of the fuel injection camshaft

单项选择题Which of the following devices is common to both mechanical and hydraulic governors?（）

A.Direct linkage between the ball-head and fuel rack
B.A servomotor
C.A compensating device
D.Flyweights