单选题Mechanical lubricators for diesel engine cylinders are usually small reciprocating pumps which are （）.A operated manually once an hourB operated until the engine has startedC placed into operation only at maximum loadD adjustable to meet lubrication re

operated manually once an hour

operated until the engine has started

placed into operation only at maximum load

adjustable to meet lubrication requirements

fine atomization

high temperature

good mixing of fuel and air

all of the above

in such cases, the air supply is no longer optimal, the thermal load will be higher

governor hunting will occur

torsional vibrations as other mechanical vibrations may occur

all of the above are correct

quantity of air it takes in and retains in the cylinders during a given time period

proportion of trapped air that is utilized in the combustion process

thermodynamic efficiency of the engine cycle

all of the above

vacuum pressure

specific gravity

heat

viscosity

caused by retarded injection timing

caused by a mechanical defect in one cylinder

caused by high fuel injection pressures

normal for these conditions

testing for the mechanical load and the thermal load

inspecting thermal and mechanical condition of the engine

inspecting each system and exhaust temperature

testing for compress pressure and explosion pressure

turn engine with jacking gear

drain filters and strainers and bleed off water at each injection pump

use ether to start the engine with blow-down valves open

blow through the cylinders and fuel lines with a drying agent