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单选题
Dirt lodged on the nozzle valve seat of a fuel injection nozzle will cause（）
A
erosion and cratering of the nozzle orifices
B
fuel leakage into the nozzle drain line
C
fuel leakage before and after injection
D
insufficient fuel delivery though that nozzle
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更多 “单选题Dirt lodged on the nozzle valve seat of a fuel injection nozzle will cause（）A erosion and cratering of the nozzle orificesB fuel leakage into the nozzle drain lineC fuel leakage before and after injectionD insufficient fuel delivery though that nozzle” 相关考题
考题
The plunger in a jerk pump is rotated until the release port is uncovered If the port remains uncovered all of the time, which of the listed operations will occur?A.No fuel will be deliveredB.The maximum effective stroke will be attainedC.The fuel delivered to the cylinder will be excessiveD.The injection nozzle will overheat and carbonize
考题
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
考题
Springs in fuel injectors will become not strong enough to work because______.A.the injector opens at a lower pressure than designedB.the needle valve and seat wear outC.the nozzle holes wear outD.long time in use
考题
_______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
考题
单选题The consistent burning of fuel oil with a high sulfur content in a diesel engine will result in （）A
clogged fuel injection pumpsB
increased cylinder liner wearC
intake valve stem corrosionD
varnish deposit on pistons
考题
单选题Movement of the pump control rack in a fuel injection system using individual plunger-type pumps （）A
changes the position of the fuel inlet portsB
changes the length of the pump strokeC
varies the quantity of fuel deliveredD
varies the compression of the delivery valve spring
考题
单选题The primary function of a fuel delivery check valve assembly is to（）A
deliver proper fuel quantity to the injection nozzleB
provide rapid fuel injection cutoffC
control fuel quantity entering the pump bodyD
control fuel pressure delivered to the combustion chamber
考题
单选题Heat damage to fuel injection nozzles on small high-speed diesel engines, can be prevented by（）A
employing fuel oil as a cooling mediumB
preventing hard carbon deposit on nozzle tipsC
avoiding fuel oil temperature exceeding builder’s specificationD
ensuring good metallic contact between nozzles and cylinder heads
考题
单选题If the needle valve in a fuel injection nozzle sticks open （）.A
no fuel will be delivered through the nozzleB
the nozzle will overheat and crackC
time of injection will changeD
fuel will leak into the drain line
考题
单选题If a single cylinder relief valve on a diesel engine lists frequently while the engine is running, the cause may be an （）A
excessively late injection timing for each cylinderB
incorrectly adjusted intake valve timingC
incorrectly adjusted fuel injectorD
incorrectly adjusted intake valve clearance
考题
单选题In the common rail system, excessive pressure in the header may be caused by （）A
improper adjustment of the bypass valveB
a dribble in the fuel injection nozzleC
insufficient leak-off through injection nozzle packingD
a malfunctioning injection nozzle
考题
单选题During the fuel injection period, fuel pressure must exceed cylinder gas pressure to （）.A
ensure penetration and distribution of the fuel in the combustion chamberB
ensure the needle valve is flushed clean during each injectionC
prevent combustion gas blowback into the open needle valveD
prevent reflected pressure waves when the needle valve closes
考题
单选题The key feature of the Sulzer RT-flex system is that it gives complete freedom in the and operation of fuel injection and exhaust valve actuation（）A
meteringB
controlC
usingD
timing
考题
单选题Valve lash, or clearance refers to the （）A
clearance between the top of the valve stem and the rocker armB
compression of the valve springsC
clearance between the valve seat inserts and the headD
out of roundness of the fuel injection cams
考题
单选题Which of the following problems may occur if the opening pressure of a fuel injection nozzle is greater than specified by the engine manufacturer?（）A
The amount of fuel injected will be increasedB
The start of injection will be retardedC
The nozzle will permit fuel to dribbleD
The spray pattern will be distorted
考题
单选题A fuel injection valve opening at pressure lower than normal will result in（）.A
late fuel injectionB
early fuel injectionC
high exhaust temperature from that cylinderD
decreased effective stroke from that injector
考题
单选题The purpose of the delivery check valve used in a diesel fuel injection jerk pump is to （）.A
assist in a quick cutoff of fuel injectionB
allow oil backflow from the injector to the helixC
reduce fuel oil pressure between injection strokesD
meter the quantity of fuel delivered
考题
单选题The quantity of oil injected into the cylinder can be regulated （）.A
by turning the pump plungerB
by vary the fuel valve spring forceC
by no means by controlling the governorD
by enlarging or diminishing the injection hole
考题
单选题Which of the following problems will occur if the needle valve in a fuel injection nozzle sticks in the open position?（）A
Fuel injection timing will changeB
Nozzle operation will be unaffectedC
Fuel will leak into the drain lineD
Fuel will not be delivered
考题
单选题Faulty operation of diesel engine fuel injection nozzles can be a direct cause of（）.A
excessive fuel nozzle holder coolingB
sediment in the fuel supplyC
distortion of the fuel spray patternD
improper atomization of the fuel
考题
单选题Faulty operation of diesel engine fuel injection nozzles can be directly caused by （）.A
water in the fuel oil supplyB
excessive fuel nozzle holder coolingC
a distorted fuel spray patternD
leakage past the plunger into the oil drain
考题
单选题In the cylinder of a diesel engine fuel is ignited by the（）A
spark from a plug in the pre-combustion chamberB
electrical discharge from the distributorC
heat of compression within the cylinderD
heat from the fuel injection nozzle
考题
单选题When a fuel injection nozzle overheats, which of the problems listed can be expected?（）A
The fuel metering will varyB
The fuel will explodeC
The cylinder head will crackD
The engine will stop
考题
单选题The major cause of problems occurring with fuel injection equipment is（）A
incorrect replacement of barrels and plungers of jerk pumpsB
overheating of the nozzle orificesC
cracked pump housingsD
dirt in the fuel
考题
单选题High cylinder firing pressure, accompanied by low exhaust temperature, can result from （）A
improper fuel rack positingB
lengthy exhaust valve durationC
extend operation at light loadD
excessively early injection timing
考题
单选题Which of the fuel injection systems listed uses a spring loaded differential spray needle valve and individual pump for each cylinder?（）A
Common-rail injectionB
Air injectionC
Jerk pump injectionD
Distribution injection
考题
单选题If the plunger or barrel of a fuel injection jerk pump becomes damaged,（）A
only the replacement of the entire pump would be acceptableB
the injection pump and injection nozzle must be replacedC
either the barrel or plunger must be replacedD
the barrel and plunger must be replaced as a unit
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