Diesel Mechanic RRB Exam MCQs

1. What is the function of a diesel engine’s turbocharger?
a) Cooling the engine
b) Increasing air pressure in the combustion chamber
c) Igniting the fuel
d) Controlling exhaust emissions

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Answer: b) Increasing air pressure in the combustion chamber

2. Which of the following is the primary fuel used in diesel engines?
a) Gasoline
b) Diesel fuel
c) Propane
d) Natural gas

Answer: b) Diesel fuel

3. What is the purpose of a fuel injector in a diesel engine?
a) Mixing fuel and air
b) Delivering fuel into the combustion chamber
c) Controlling exhaust gases
d) Cooling the engine

Answer: b) Delivering fuel into the combustion chamber

4. Which engine component is responsible for converting reciprocating motion into rotary motion in a diesel engine?
a) Crankshaft
b) Piston
c) Camshaft
d) Connecting rod

Answer: a) Crankshaft

5. What is the purpose of the glow plug in a diesel engine?
a) Igniting the fuel
b) Improving fuel efficiency
c) Reducing exhaust emissions
d) Preheating the combustion chamber

Answer: d) Preheating the combustion chamber

6. What is the typical compression ratio in a diesel engine?
a) 8:1
b) 10:1
c) 14:1
d) 18:1

Answer: c) 14:1

7. What is the purpose of the intercooler in a turbocharged diesel engine?
a) Cooling the engine
b) Increasing air pressure
c) Cooling the compressed air
d) Enhancing exhaust flow

Answer: c) Cooling the compressed air

8. Which type of diesel engine uses a separate chamber for combustion of fuel and air before entering the main combustion chamber?
a) Direct injection
b) Indirect injection
c) Common rail injection
d) Unit injector

Answer: b) Indirect injection

9. What is the purpose of the governor in a diesel engine?
a) Controlling fuel injection
b) Regulating engine speed
c) Monitoring exhaust emissions
d) Cooling the engine

Answer: b) Regulating engine speed

10. What is the function of the exhaust gas recirculation (EGR) system in a diesel engine?
a) Reducing nitrogen oxide emissions
b) Enhancing fuel combustion
c) Increasing power output
d) Cooling the exhaust gases

Answer: a) Reducing nitrogen oxide emissions

11. What does the term “CI engine” stand for in the context of diesel engines?
a) Compression Ignition
b) Combustion Injection
c) Carburetor Injection
d) Centrifugal Ignition

Answer: a) Compression Ignition

12. What role does the alternator play in a diesel engine system?
a) Charging the battery
b) Providing air for combustion
c) Controlling fuel injection
d) Lubricating engine components

Answer: a) Charging the battery

13. In a diesel engine, what is the purpose of the timing belt or chain?
a) Regulating engine speed
b) Transmitting power to the wheels
c) Synchronizing valve and piston movements
d) Controlling exhaust emissions

Answer: c) Synchronizing valve and piston movements

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14. What is the function of the flywheel in a diesel engine?
a) Controlling fuel injection
b) Storing energy and smoothing engine operation
c) Reducing exhaust emissions
d) Preheating the combustion chamber

Answer: b) Storing energy and smoothing engine operation

15. Which of the following is a common method for cooling a diesel engine?
a) Radiator
b) Turbocharger
c) Intercooler
d) Crankshaft

Answer: a) Radiator

16. What is the purpose of the oil filter in a diesel engine?
a) Cooling the engine
b) Filtering contaminants from the oil
c) Increasing air pressure in the combustion chamber
d) Igniting the fuel

Answer: b) Filtering contaminants from the oil

17. Which part of the diesel engine is responsible for converting linear motion into rotary motion?
a) Piston
b) Crankshaft
c) Camshaft
d) Connecting rod

Answer: b) Crankshaft

18. What is the primary purpose of the air filter in a diesel engine?
a) Cooling the air
b) Increasing air pressure
c) Filtering contaminants from the air
d) Controlling exhaust emissions

Answer: c) Filtering contaminants from the air

19. In a diesel engine, what is the function of the camshaft?
a) Controlling fuel injection
b) Synchronizing valve and piston movements
c) Storing energy
d) Cooling the engine

Answer: b) Synchronizing valve and piston movements

20. What is the purpose of the differential in a diesel powered vehicle?
a) Distributing power to the wheels
b) Regulating engine speed
c) Controlling exhaust emissions
d) Cooling the engine

Answer: a) Distributing power to the wheels

11. What does the term “bore” refer to in a diesel engine specification?
a) Engine displacement
b) Cylinder diameter
c) Stroke length
d) Compression ratio

Answer: b) Cylinder diameter

12. In a four stroke diesel engine, during which stroke does the actual power stroke occur?
a) Intake stroke
b) Compression stroke
c) Power stroke
d) Exhaust stroke

Answer: c) Power stroke

13. What is the purpose of the crankcase ventilation system in a diesel engine?
a) Cooling the engine
b) Preventing oil contamination
c) Enhancing fuel combustion
d) Reducing exhaust emissions

Answer: b) Preventing oil contamination

14. What is the role of the camshaft in a diesel engine?
a) Connecting the piston to the crankshaft
b) Opening and closing engine valves
c) Controlling fuel injection timing
d) Cooling the engine

Answer: b) Opening and closing engine valves

15. Which of the following is a common type of diesel engine lubrication system?
a) Splash lubrication
b) Forced feed lubrication
c) Dry sump lubrication
d) All of the above

Answer: d) All of the above

16. What is the primary purpose of the flywheel in a diesel engine?
a) Cooling the engine
b) Balancing the crankshaft
c) Controlling exhaust emissions
d) Increasing fuel efficiency

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Answer: b) Balancing the crankshaft

17. What is the function of the thermostat in a diesel engine cooling system?
a) Regulating engine speed
b) Monitoring exhaust emissions
c) Controlling fuel injection
d) Regulating coolant temperature

Answer: d) Regulating coolant temperature

18. Which of the following is a common type of diesel engine valve mechanism?
a) Rocker arm
b) Pushrod
c) Overhead camshaft
d) All of the above

Answer: d) All of the above

19. What is the purpose of the differential in a diesel powered locomotive?
a) Steering the locomotive
b) Distributing power to the wheels
c) Cooling the engine
d) Regulating fuel injection

Answer: b) Distributing power to the wheels

20. What does the term “stroke” refer to in a diesel engine?
a) Cylinder diameter
b) Piston movement
c) Combustion duration
d) Compression ratio

Answer: b) Piston movement

21. What is the primary function of the alternator in a diesel locomotive?
a) Cooling the engine
b) Generating electrical power
c) Controlling fuel injection
d) Regulating coolant temperature

Answer: b) Generating electrical power

22. In a diesel engine, what is the purpose of the air filter?
a) Cooling the incoming air
b) Increasing air pressure
c) Filtering out impurities from the air
d) Preheating the combustion chamber

Answer: c) Filtering out impurities from the air

23. What is the primary function of the timing belt or chain in a diesel engine?
a) Cooling the engine
b) Balancing the crankshaft
c) Synchronizing engine components
d) Regulating coolant temperature

Answer: c) Synchronizing engine components

24. Which type of diesel engine combustion system has the fuel injected directly into the combustion chamber?
a) Indirect injection
b) Common rail injection
c) Direct injection
d) Unit injector

Answer: c) Direct injection

25. What is the purpose of the oil cooler in a diesel engine?
a) Cooling the engine
b) Reducing friction in the crankshaft
c) Enhancing fuel combustion
d) Regulating oil viscosity

Answer: d) Regulating oil viscosity

26. What does the term “compression ignition” refer to in the context of diesel engines?
a) Ignition by spark plug
b) Ignition by compression heat
c) Ignition by preheating
d) Ignition by fuel injection

Answer: b) Ignition by compression heat

27. What is the purpose of the fuel filter in a diesel engine?
a) Cooling the engine
b) Filtering out impurities from the fuel
c) Controlling fuel injection
d) Regulating coolant temperature

Answer: b) Filtering out impurities from the fuel

28. What is the role of the transmission in a diesel powered vehicle?
a) Regulating engine speed
b) Distributing power to the wheels
c) Cooling the engine
d) Controlling fuel injection

Answer: b) Distributing power to the wheels

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29. Which type of diesel engine has a common fuel rail supplying fuel to all cylinders?
a) Indirect injection
b) Common rail injection
c) Direct injection
d) Unit injector

Answer: b) Common rail injection

30. What is the purpose of the exhaust manifold in a diesel engine?
a) Cooling the engine
b) Distributing air to the cylinders
c) Collecting and directing exhaust gases
d) Regulating coolant temperature

Answer: c) Collecting and directing exhaust gases

31. What is the primary function of the fuel pump in a diesel engine?
a) Cooling the engine
b) Filtering the fuel
c) Pressurizing and delivering fuel to injectors
d) Regulating coolant temperature

Answer: c) Pressurizing and delivering fuel to injectors

32. In a diesel engine, what is the purpose of the glow plug controller?
a) Regulating engine speed
b) Controlling fuel injection
c) Monitoring exhaust emissions
d) Preheating the glow plugs

Answer: d) Preheating the glow plugs

33. What is the function of the crankcase heater in a diesel engine?
a) Cooling the engine
b) Regulating coolant temperature
c) Preheating the engine oil
d) Reducing engine vibrations

Answer: c) Preheating the engine oil

34. Which type of diesel engine valve is responsible for releasing excess pressure in the combustion chamber?
a) Intake valve
b) Exhaust valve
c) Pressure relief valve
d) Overhead valve

Answer: c) Pressure relief valve

35. What is the purpose of the turbo intercooler in a turbocharged diesel engine?
a) Cooling the engine
b) Cooling the compressed air
c) Enhancing fuel combustion
d) Regulating coolant temperature

Answer: b) Cooling the compressed air

36. In a diesel engine, what does the term “governor hunting” refer to?
a) Unstable engine speed oscillations
b) Controlling fuel injection
c) Regulating coolant temperature
d) Monitoring exhaust emissions

Answer: a) Unstable engine speed oscillations

37. What is the primary purpose of the catalytic converter in a diesel vehicle?
a) Reducing nitrogen oxide emissions
b) Filtering particulate matter from the exhaust
c) Enhancing fuel combustion
d) Regulating oil viscosity

Answer: a) Reducing nitrogen oxide emissions

38. Which of the following is a common type of diesel engine cooling system?
a) Air cooled system
b) Oil cooled system
c) Water cooled system
d) All of the above

Answer: c) Water cooled system

39. What is the function of the ECU (Engine Control Unit) in a modern diesel engine?
a) Regulating engine speed
b) Controlling fuel injection
c) Monitoring exhaust emissions
d) Cooling the engine

Answer: b) Controlling fuel injection

40. What is the purpose of the PCV (Positive Crankcase Ventilation) valve in a diesel engine?
a) Cooling the engine
b) Reducing oil consumption
c) Enhancing fuel combustion
d) Regulating exhaust emissions

Answer: b) Reducing oil consumption


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