单项选择题
A.the start fails
B.the fuel pumps will be put into operation
C.the fuel valves are damaged
D.the combustion process will take over
单项选择题 The engine may lose power or slow down during running, when this occurs, the first cause possible may be hot bearings and （） of the pistons in the cylinders.
单项选择题 The engine is started with （） supplied from air receivers.
单项选择题 The engine is reversed by axial displacement of the camshafts In order for this to be carried out, the cams are （） with inclined transition faces.