單項選擇題Which of the following conditions could contribute to the cracking of a diesel engine cylinder head?（）

A.Leaking seal ring
B.Insufficient heat transfer from the exhaust valves
C.Block cooling water passages to the head
D.Excessive scavenging air provided to the engine


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1.單項選擇題The cetane rating of diesel fuel is an indication of the（）

A.ignition quality of the fuel
B.calorific value of the fuel
C.flash point of the fuel
D.rate of fuel consumption

2.單項選擇題The cetane number of a diesel fuel oil indicates its（）

A.Viscosity
B.acid content
C.heating value
D.ignition quality

3.單項選擇題Which of the listed factors will indicate the most about the ability of a fuel to ignite in a diesel engine?（）

A.Viscosity
B.Sulfur content
C.Pour point
D.Cetane number

4.單項選擇題Why will a turbocharger diesel engine produce black smoke if excessive additional load is applied too quickly?（）

A.Exhaust energy would draw excess air
B.The inertia of the turbocharger rotor causes a time lag which delays the turbocharger speed increase
C.Exhaust gas pumping losses are increased due to turbine windage
D.Exhaust gas back pressure falls slightly due to increased nozzle action

5.單項選擇題Cold weather starting of a diesel engine is more difficult than warm weather starting due to（）

A.use of low viscosity oil in cold weather
B.increased moisture content of inlet air in cold weather
C.increased drag of pistons and bearings due to increased oil viscosity
D.higher compression pressures reached due to smaller clearances existing in the engine during cold weather