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
Indirect cooling of fuel injector nozzle holders for diesel engines is accomplished primarily by （）.
A
heat conduction into the injected fuel oil
B
heat conduction into the water jacket wall
C
water circulation through passages in the holder
D
fuel oil circulation through passages in the holder
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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
Indirect cooling of fuel injector nozzle holders for diesel engines is accomplished primarily byA.heat conduction into the injected fuel oilB.heat conduction into the water jacket wallC.water circulation through passages in the holderD.fuel oil circulation through passages m the holder
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
Cooling water is circulated through______in some injectors.A.the nozzleB.the nozzle tipC.the internal passagesD.the fuel re-circulated
_______can be a direct cause of faulty operation of diesel engine fuel injection nozzles.A.Excessive fuel nozzle holder coolingB.Sediment in the fuel supplyC.Distortion of the fuel spray patternD.Improper atomization of the fuel
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Fuel oil discharged to the diesel engine cylinder is atomized at the （）AturbochargerBinjection nozzle tipCcarburetorDfuel oil pump
单选题White smoke exhausting from a diesel engine can be caused by （）Alow combustion temperatureBa leaking fuel nozzle check valveClate fuel injectionDplugged oil-scraper ring hole
单选题Heat damage to fuel injection nozzles on small high-speed diesel engines, can be prevented by（）Aemploying fuel oil as a cooling mediumBpreventing hard carbon deposit on nozzle tipsCavoiding fuel oil temperature exceeding builder’s specificationDensuring good metallic contact between nozzles and cylinder heads
单选题A leaking diesel engine fuel injector will cause（）Aprolonged maintenance intervalsBimproved atomizationCgreater fuel economyDincomplete combustion
单选题As the plunger moves up, the ports are closed and the fuel （） and delivered to the injector nozzle at very high pressure.Abeing compressedBto be pumped upCis pressurizedDare built up
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In a unit injector the amount of fuel that will be forced through the spray nozzle on each stroke of the plunger depends on （）Athe pump supply pressureBthe slope of the fuel camChow the plunger is rotatedDthe number of sleeve segments engaged with the rack
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A defective injector nozzle in a propulsion diesel engine can cause（）Aengine power lossesBsmoking due to unburned fuelChigh exhaust temperature readingsDall of the above
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Faulty operation of diesel engine fuel injection nozzles can be a direct cause of（）.Aexcessive fuel nozzle holder coolingBsediment in the fuel supplyCdistortion of the fuel spray patternDimproper atomization of the fuel
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Faulty operation of diesel engine fuel injection nozzles can be directly caused by （）.Awater in the fuel oil supplyBexcessive fuel nozzle holder coolingCa distorted fuel spray patternDleakage past the plunger into the oil drain
单选题In the cylinder of a diesel engine fuel is ignited by the（）Aspark from a plug in the pre-combustion chamberBelectrical discharge from the distributorCheat of compression within the cylinderDheat from the fuel injection nozzle
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