单项选择题
A.cam rollers on the camshaft
B.spring force
C.air pressure on top of the valve differential piston
D.air pressure on the bottom of the valve differential piston
单项选择题 The depth of fuel oil in a tank is normally measured through the（）
单项选择题 Which of the following methods is used to prevent throttling of compressed air through the diesel engine air starting valves?（）
单项选择题 Small crack in the crankshaft bearing surface of a diesel engine are an indication of（）