单项选择题
A.maintain low pH in the cooling water B.reduce the cooling water temperature C.increase cooling water hardness D.form a protective film on metal surfaces
Fuel droplets injected into a diesel engine cylinder mu...
单项选择题Fuel droplets injected into a diesel engine cylinder must have adequate penetration to （）
A.prolong the ignition delay period B.ensure the beginning of fuel injection C.thoroughly utilize the air charge D.allow controlled fuel combustion
The primary function of a fuel delivery check valve ass...
单项选择题The primary function of a fuel delivery check valve assembly is to（）
A.deliver proper fuel quantity to the injection nozzle B.provide rapid fuel injection cutoff C.control fuel quantity entering the pump body D.control fuel pressure delivered to the combustion chamber
For any piston ring to operate smoothly without scuffin...
单项选择题For any piston ring to operate smoothly without scuffing ,the ring must be （）.
A.of a material harder than the cylinder liner B.properly lubricated C.prevented from compressing D.prevented from rotating during engine operation
