单项选择题
Which of the following problems is the main source of fuel pump and injection system malfunctions?（）
A.Improper lubrication B.Air in the fuel system C.Coated fuel lines D.Excessive vibration
单项选择题 Which of the following faults would allow lube oil to enter the cooling system of a diesel engine?（）
单项选择题 Problems with the diesel engine fuel injection pump are usually caused by（）
单项选择题 Diesel engine cylinder head test cocks are used to（）
