250+ TOP MCQs on Fuel Injection System and Answers

Automotive Engine Auxiliary Systems Multiple Choice Questions on “Fuel Injection System”.

1. How are the unit injectors operated in a Common rail fuel injection system?
a) Crankshaft
b) Rocker arms
c) Belt
d) Motor
Answer: b
Clarification: The common rail fuel injection system the unit injectors are operated by rocker arms and springs similar to the engine valves. A linkage connects the control racks of all the unit injectors, so that fuel injection in all the cylinders may be equal and simultaneously controlled.

2. Which of the following is used to return the excess fuel in the rail to the fuel tank?
a) Float valve
b) Relief valve
c) Hand pump
d) Governor
Answer: b
Clarification: The excess fuel in the rail is returned to the tank by the means of a relief valve present in the circuit. Then again the fuel is taken from fuel tank by the feed pump and is supplied at low pressure through a filter, to the low-pressure common rail and therefore, to all the unit injectors.

3. Which of the following can be removed by using a hand priming lever without turning the engine on in an Individual pump fuel injection system?
a) Air bled out
b) Temperature
c) Oil
d) Coolant
Answer: a
Clarification: The pump is provided with a hand priming lever so that the diesel oil can be forced into the system and the air bled out without turning the engine. The fuel is passed through a filter and hence to the fuel injection pump.

4. Which among the following is provided in an injection pump to provide automatic speed control?
a) Filter
b) Feed pump
c) Governor
d) Injector
Answer: c
Clarification: The injection pump contains a governor which provides automatic speed control, relative to any set position of the accelerator pedal. Any excess fuel after the lubrication of the injector nozzle is returned to the fuel tank. This system can be seen in the Swaraj Mazda SL engine.

5. Which of the following types of injection is used in the Common rail fuel injection system?
a) Solid injection
b) Air injection
c) Both solid and air injection
d) Oil injection
Answer: a
Clarification: A solid injection system, only the liquid fuel is injected due to which the common rail fuel injection system and individual pump fuel injection system are an example of solid injection.

6. Along with compressed air which of the following is injected inside the cylinder?
a) Antifreeze
b) Coolant
c) Liquid fuel
d) both coolant and liquid fuel
Answer: c
Clarification: In an air injection system liquid fuel is injected along with compressed air. The air injection is less reliable and less efficient. Whereas the coolant is added inside the radiator tank to cool the engine during a long run.

7. What is the pressure range in MPa of the compressed air that has been injected in an air injection?
a) 5
b) 7
c) 6
d) 8
Answer: b
Clarification: The air injection system has a liquid fuel injected with compressed air at 7MPa due to this reason it has been obsolete. This makes the air injection system less reliable, less efficient and requires a compressor all the time.

8. How much percentage of the power output of the engine is used during the injection process in an air injection system?
a) 5
b) 10
c) 15
d) 20
Answer: b
Clarification: The air injection system is less reliable, less efficient and requires an air compressor for supplying 7MPa of compressed air with the fuel which consumes up to 10% of the power output of the engine.

9. Which of the following is the correct flow of fuel in an individual pump fuel injection system?
a) Fuel tank – filter – feed pump – injector
b) Fuel tank – filter – injector- feed pump
c) Fuel tank – feed pump – filter – injector
d) Filter- feed pump – fuel tank – injector
Answer: c
Clarification: The fuel flows from the fuel tank to the feed pump where the pressure is increased and then the fuel is filtered by the filter and then it is sent to the injector. Therefore the correct sequence of the fuel flow is fuel tank – feed pump – filer – injector.

10. What is the main function of a good fuel filter concerning the injector?
a) Faulty spraying
b) Leakage
c) Increased fuel consumption
d) Filter moisture present
Answer: d
Clarification: The abrasive matter would also cause faulty spraying and leakage in the injector thus resulting in increased fuel consumption whereas a good fuel filter should absorb any moisture and dirt present in the fuel.

11. Which of the following is used from the engine to drive a gear-driven injection pump?
a) Crankshaft
b) Camshaft
c) Motor
d) Alternator
Answer: b
Clarification: The injection pump is gear driven from the engine camshaft so that it is driven at half the engine speed. The injection pump consists of a governor which provides automatic speed control, relative to any set position of the accelerator pedal.

12. What is the range of the cranking compression pressure in the range of KP in a diesel engine?
a) 1000
b) 2000
c) 3000
d) 10000
Answer: c
Clarification: The cranking compression pressure on a diesel engine is about 3000KPa. Compression pressure is the pressure that is used to compress the charge inside the cylinder and rise it to the ignition temperature.

13. What is the range in MPa of pressure injection in diesel engines?
a) 100
b) 200
c) 300
D) 400
Answer: b
Clarification: In diesel engines, the injection pressure can reach as High as 200MPa. This high pressure is required to atomize the fuel properly for complete combustion so that the emissions can be controlled to a greater extent.