单选题When the opening pressure of a diesel fuel injector is greater than that specified by the engine manufacturer，the （）Aquantity of fuel injected is decreasedBquantity of fuel injected will always be increasedCstart of injection is advancedDduration of injection will always be greater
单选题
When the opening pressure of a diesel fuel injector is greater than that specified by the engine manufacturer，the （）
A
quantity of fuel injected is decreased
B
quantity of fuel injected will always be increased
C
start of injection is advanced
D
duration of injection will always be greater
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A smoking exhaust from an operating diesel engine could be caused by( ).A.low sulfur content in the fuelB.a loose injector inlet connectionC.late fuel injectionD.high injection pressure
If you suspect a diesel engine is misfiring due to air leakage into the fuel system, you should begin looking for the leak at theA.fuel line connections to the cylinder injection valvesB.gasket surfaces of the fuel oil filtersC.discharge fittings of the fuel injector pumpsD.suction side of the fuel oil transfer pump
第一组Older loop scavenged engines may have a single injector mounted centrally in the cylinder head. Because the exhaust valve is in the center of the cylinder head on modern uniflow scavenged engines the fuel valves (2 or 3) are arranged around the periphery of the head. The pressure at which the injector operates can be adjusted by adjusting the loading on the spring. The pressures at which the injectors operate vary depending on the engine, but can be as high as 540 bar. Some injectors have internal cooling passages in them extending into the nozzle through which cooling water is circulated. This is to prevent overheating and burning of the nozzle tip. Injectors on modern engines do not have internal cooling passages. They are cooled by a combination of the intensive bore cooling in the cylinder head being close to the valve pockets and by the fuel which is re-circulated through the injector when the follower is on the base of the cam or when the engine is stopped. As well as cooling the injector, re-circulating the fuel when the engine is stopped keeps the fuel at the correct viscosity for injection by preventing it from cooling down. Fuel injectors must be kept in good condition to maintain optimum efficiency, and to prevent conditions arising which could lead to damage within the cylinder. Injectors should be changed in line with manufacturers recommendations, overhauled and tested. Springs can weaken with repeated operation leading to the injector opening at a lower pressure than designed. The needle valve and seat can wear which together with worn nozzle holes will lead to incorrect atomization and dribbling.Modern uniflow scavenged engines have______.A.a single injector mounted in the center of the cylinder headB.several injectors mounted around the external boundary of the cylinder headC.a single injector mounted at the external boundary of the cylinder headD.several injectors mounted in the center of the cylinder head
Fuel is admitted to a diesel engine cylinder through the ______.A.injector nozzlesB.carburetorC.exhaust portsD.intake valves
单选题When the opening pressure of a diesel fuel injector is greater than that specified by the engine manufacturer，the （）Aquantity of fuel injected is decreasedBquantity of fuel injected will always be increasedCstart of injection is advancedDduration of injection will always be greater
单选题A leaking diesel engine fuel injector will cause（）Aprolonged maintenance intervalsBimproved atomizationCgreater fuel economyDincomplete combustion
单选题A sudden drop in diesel engine cylinder compression pressure can be caused by（）Aa leaking fuel injector nozzleBa clogged air filterCexcessively early fuel injectionDmalfunctioning valves
单选题The fuel injector injects a fine spray of fuel into the hot air and combustion （）, producing much high pressure in the gases.Ahas begunBtakes placeCoccursDhappens
单选题A practical way of checking for excessive fuel injection in one cylinder of an operating diesel engine is to （）Afeel the high pressure fuel lineBcheck the cylinder exhausts for white smoke frequentlyCcheck the cylinder exhaust temperatureDisolate each cylinder and inspect the injector
单选题When the opening pressure of a diesel engine fuel injector is greater than that specified by the engine manufacturer, which of the following problems can be expected?（）AQuantity of fuel injected tends to be decreasedBQuantity of fuel injected will always be increasedCStart of injection tends to be advancedDDuration of injection will always greater
单选题A smoking exhaust from an operating diesel engine could be caused by （）Alow sulfur content in the fuelBa loose injector inlet connectionClate fuel injectionDhigh injection pressure
单选题To successfully reduce an excessively high diesel engine exhaust gas temperature, you should （）.Areduce the engine driven fuel pump outlet pressureBretard the fuel injector timing to reduce powerCincrease the fuel rack settingDreduce the load on the engine
单选题The （） in the injector will lift at a pre-set pressure which ensures that the fuel will atomize once it enters the cylinder.Aneedle valveBnozzlesCpistonDspring
单选题Which one is not the normal operation for boiler shutdown?（）ACarry out soot blowing if permissibleBChange fuel supply to diesel oilCClose steam stop valves on boiler when pressure is reducedDDrain boiler empty when it has cooled down
单选题If a diesel engine is smoking excessively under load, the cause could be （）Alow exhaust back pressureBearly fuel injection in one of the cylindersCcompression pressure in one of the cylindersDplugged injector holes
单选题A change in the quality of fuel atomization by a diesel engine fuel injector would be caused by a/an （）Aincrease in engine speedBincrease in cylinder turbulenceCleaking needle valveDreduction in cylinder turbulence
单选题Injection lag in a diesel engine may be caused by（）Aa higher cetane number of fuel oilBthe diesel fuel used having a high viscosityCmechanical rigidity in the lube pump mechanismDa decrease rigidity in the fuel pump delivery pressure
单选题The amount of fuel injection into a diesel engine cylinder by a unit injector, is controlled by（）Athe firing pressure in the cylinderBa metering helix inside the pumpCvarying the physical length of the plunger strokeDvarying the clearance between the injector cam and the injector rocker arm
单选题A fuel injection valve opening at pressure lower than normal will result in（）.Alate fuel injectionBearly fuel injectionChigh exhaust temperature from that cylinderDdecreased effective stroke from that injector
单选题The purpose of the delivery check valve used in a diesel fuel injection jerk pump is to （）.Aassist in a quick cutoff of fuel injectionBallow oil backflow from the injector to the helixCreduce fuel oil pressure between injection strokesDmeter the quantity of fuel delivered
单选题Indirect cooling of fuel injector nozzle holders for diesel engines is accomplished primarily by （）.Aheat conduction into the injected fuel oilBheat conduction into the water jacket wallCwater circulation through passages in the holderDfuel oil circulation through passages in the holder
单选题A distorted spray pattern from a fuel injector can cause a diesel engine to have （）Ahigher firing pressureBmore power outputClower fuel pressureDless power output
单选题Low compression pressure in a diesel engine may be the result of （）Ainsufficient fuel supply due to fuel pump valves sticking or leakingBexcessive mechanical clearance between the piston crown and cylinder headCexcessively worn fuel pump plungerDexcessive exhaust back pressure
单选题One remedy for a high firing pressure, in addition to a high exhaust temperature in one cylinder of a diesel engine, is to （）Aincrease scavenge air pressureBreduce fuel booster pump pressureCadjust the fuel rackDretard fuel injector timing
单选题A sudden drop in compression pressure in one cylinder of a diesel engine can be caused by（）Aa leaking fuel injector nozzleBa clogged air filterCexcessively early fuel injectionDmalfunctioning valves
单选题If you suspect a diesel engine is misfiring due to air leakage into the fuel system, you should begin looking for the leak at the （）Afuel line connections to cylinder injection valvesBgasket surfaces of the fuel oil filtersCdischarge fitting of the fuel injector pumpsDsuction side of the fuel oil tran
单选题When comparing different fuels for different engines, the ignition quality of diesel fuel oils becomes a less critical consideration as （）Athe amount of lube oil additives increaseBpiston speeds increaseCinjection pressure decreaseDengine speeds decrease
单选题The minimum fuel oil delivery pressure required for diesel engine injection depends primarily on the（）Adegree of cylinder air turbulenceBfiring pressure in the engineCquality of fuel to be injectedDduration of the ignition delay period