Class 12 Automotive Chapter 2 Serviceability, Replacement or Repair of Engine Components

Class 12 Automotive Chapter 2 Serviceability, Replacement or Repair of Engine Components Solutions English Medium As Per AHSEC New Syllabus to each chapter is provided in the list so that you can easily browse through different chapters Class 12 Automotive Chapter 2 Serviceability, Replacement or Repair of Engine Components Question Answer and select need one. Class 12 Automotive Chapter 2 Serviceability, Replacement or Repair of Engine Components Notes Download PDF. AHSEC Class 12 Elective Automotive Question Answer English Medium.

Class 12 Automotive Chapter 2 Serviceability, Replacement or Repair of Engine Components

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Also, you can read the NCERT book online in these sections Solutions by Expert Teachers as per Central Board of Secondary Education (CBSE) Book guidelines. AHSEC Class 12 Elective Automotive Textual Solutions are part of All Subject Solutions. Here we have given AHSEC Class 12 Automotive Textbook Solutions English Medium for All Chapters, You can practice these here.

Serviceability, Replacement or Repair of Engine Components

Chapter: 2

A. Fill in the blanks:

1. The valve mechanism controls the submission of inlet gases and emission of exhaust gases in relation to the rotation of the ________________. 

Ans: Cam shaft.

2. Valve ______________ is necessary to diagnose leakages of combustion gases and improve engine performance. 

Ans: Timing.

3. During the valve lapping operation, abrasive/emery paste is applied on the valve face, and the lapping stick is turned in both clockwise and anticlockwise directions to ensure proper sealing between the valve and ________________. 

Ans: Valve seat.

4. The Overhead Cam (OHC) mechanism consumes less engine power for valve operation and is located at the _________________. 

Ans: Cylinder head.

B. Multiple Choice Questions:

1. Which of the following components controls the timing and quantity of gas or vapor flow into an engine? 

(a) Piston rings. 

(b) Rocker arm.

(c) Valve. 

(d) Camshaft. 

Ans: (d) Camshaft.

2. What is the primary reason for conducting a compression test of an engine’s valve mechanism? 

(a) To measure fuel efficiency.

(b) To check for coolant leaks. 

(c) To assess valve leakage. 

(d) To evaluate oil pressure. 

Ans: (c) To assess valve leakage. 

3. In an Overhead Cam (OHC) mechanism, where is the camshaft fixed. 

(a) In the crankcase. 

(b) In the cylinder head. 

(c) On the rocker arm. 

(d) In the valve guide. 

Ans: (b) In the cylinder head.

4. What is the purpose of the valve lapping operation during reconditioning? 

(a) To measure valve leakage. 

(b) To replace damaged valves.

(c) To adjust valve tappet clearance. 

(d) To ensure proper sealing between the valve and valve seat.

Ans: (d) To ensure proper sealing between the valve and valve seat.

C. Answer the following questions:

1. What is poppet valve?

Ans: The valves used in internal combustion engines are usually known as poppet valves. A poppet valve is a valve typically used to control the timing and quantity of gas or vapour flow into an engine.

2. How many kinds of valve used in IC Engine? 

Ans: Valve mechanism are classified as given below:

(i) Overhead valve mechanism (OHV).

(ii) Overhead Cam mechanism (OHC).

3. What are the purposes of a valve?

Ans: It controls the submission of inlet gases and emission of exhaust gases at the right time in relation to the rotation of the cam shaft.

4. Briefly describe a function of a valve & draw its line diagrams with details. 

Ans: Valve mechanism: It controls the submission of inlet gases and emission of exhaust gases at the right time in relation with the rotation of the cam shaft.

Line diagrams: 

5. What are the seat angles & why it is required? 

Ans: (i) Measure the angle of the valve seat with the help of a bevel protractor. 

(ii) Check the margin of the valve seat; if it is less than 2 mm replace the valve seat. 

(iii) If it is more than 2 mm, then it is suggested to carry out valve seat grinding operation. 

(iv) Select grinder/ cutter of appropriate size and angle. 

(v) Fix the holder and pilot to the grinding stone/cutter. 

(vi) Now grind the valve seat with a machine or manually and cut the valve seat to get the required angle.

6. Which part control opening & closing of a valve? 

Ans: The valve advance mechanism controls the supply of fuel and increases the engine efficiency at high speeds.

7. Write the name of the tools required for valve seat grinding. 

Ans: Select grinder/cutter of appropriate size and angle. Fix the holder and pilot to the grinding stone/cutter.

A. Fill in the blanks:

1. The primary functions of piston rings in an internal combustion engine are to seal the ________________ so that there is no transfer of combustion gases from the chamber to the crankcase. 

Ans: Combustion chamber.

2. The top two rings in most automobile engines are known as _________________, while the lower ring is an oil ring responsible for controlling oil supply. 

Ans: Compression rings.

3. Piston rings are subjected to wear due to movement within the cylinder bore as the piston moves from _______________ to Bottom Dead Centre. 

Ans: Top Dead Centre.

4. During the inspection of piston clearance in a multi-cylinder engine, a set of tools including spanners, a micrometer, and a _______________ gauge is used to ensure correct gaps and clearances. 

Ans: Feeler.

B. Multiple Choice Question:

1. What is the main function of piston rings in an internal combustion engine? 

(a) To increase fuel efficiency.

(b) To regulate exhaust emissions.

(c) To cool down the engine components.

(d) To seal the combustion chamber and prevent gas leakage.

Ans: (d) To seal the combustion chamber and prevent gas leakage.

2. Which type of piston ring is responsible for controlling the supply of oil to the cylinder liner? 

(a) Compression ring. 

(b) Exhaust ring. 

(c) Oil ring.

(d) Power ring.

Ans: (c) Oil ring.

3. What is the primary reason for the wear of piston rings in an engine? 

(a) Movement within the cylinder bore during engine cycles. 

(b) Inadequate cooling. 

(c) Excessive lubrication. 

(d) Irregular combustion. 

Ans: (a) Movement within the cylinder bore during engine cycles.

4. What is the purpose of inspecting the end gap of a piston ring? 

(a) To measure the thickness of the ring. 

(b) To check for wear on the cylinder bore.

(c) To ensure proper alignment of the piston ring.

(d) To determine the oil consumption rate of the engine.  

Ans: (c) To ensure proper alignment of the piston ring.

C. Answer the following questions:

1. How many types of rings used in piston? 

Ans: Generally, three types of rings are used in a piston:

(i) Top compression ring.

(ii) Second compression ring.

(iii) Oil control ring.

2. How much the clearance provided in the cylinder bore? 

Ans: The clearance depends on the engine design, but typically it is about 0.03 mm to 0.08 mm (for small engines) and can go up to 0.10 mm or slightly more for bigger engines. This clearance ensures smooth movement and compensates for thermal expansion.

3. What are the functions of compression rings?

Ans: Compression rings are designed to withstand more pressure and temperature. The piston ring expands and contracts during compression and exhaust stroke. This movement of the ring reduces the width of the ring and increases the end gap. Further it reduces elasticity/tension causing piston ring wear.

4. What are the functions of oil control ring? 

Ans: The lower ring is used for controlling the supply of oil to the liner, which lubricates the piston skirt and the compression rings.

5. What is the position of the ring in the piston? 

Ans: Most automobile engine pistons have three rings: The top two rings are compression rings and lower ones are oil rings.

A. Fill in the blanks:

1. In an engine, the cylinder liner, also known as a ____________, lines the inside of the cylinder to protect it from wear and damage. 

Ans: Bore sleeve.

2. If a connecting rod is damaged beyond repair, it needs to be ____________ with a new one. 

Ans: Replaced.

3. One of the indicators of worn-out engine bearings is the presence of ____________ in the oil. 

Ans: Metal particles.

4. Inspecting the ____________ of the crankshaft is done using a dial gauge to check for runout or bending.

Ans: Crankshaft.

B. Multiple Choice Questions: 

1.What is the purpose of a cylinder liner or bore sleeve in an engine? 

(a) To hold the spark plugs. 

(b) To line the inside of the cylinder and protect it.

(c) To connect the piston to the crankshaft. 

(d) To control the flow of coolant.

Ans: (b) To line the inside of the cylinder and protect it.

2. What is the primary reason for inspecting the cylinder liner? 

(a) To check the color of the liner. 

(b) To ensure proper coolant flow. 

(c) To measure the piston size. 

(d) To identify wear, scratches, or damage. 

Ans: (d) To identify wear, scratches, or damage. 

3.What could cause scratches on a cylinder liner? 

(a) Excessive coolant flow.

(b) Incorrect piston size. 

(c) Piston ring sticking. 

(d) Too much engine oil.

Ans: (c) Piston ring sticking.

4. The connecting rod in an engine serves to: 

(a) Direct the flow of air. 

(b) Convert rotational motion to up-and-down motion. 

(c) Hold the fuel injectors. 

(d) Control exhaust gas emissions.

Ans: (b) Convert rotational motion to up-and-down motion.

C. Answer the following questions:

1. What is the function of connecting rod?

Ans: The connecting rod connects the piston to the crankshaft and converts the reciprocating motion of the piston into rotary motion of the crankshaft.

2. Why do some connecting rod have hole drilled from small end to the big end bearing?

Ans: To provide lubrication, some connecting rods have holes drilled from the small end to the big end bearing.

3. Which parts are connected to the small end of the connecting rod? 

Ans: The small end of the connecting rod is connected with the piston pin.

4. Which part of connecting rod is connected with crankshaft?

Ans: The big end of the connecting rod is connected with the crankshaft.

5. How to check bend in connecting rod?

Ans: Always replace the bend or twisted connecting rod.

6. How to check clearance between connecting rod and crankshaft?

Ans: Inspect oil clearance/bearing clearance by using a plastic gauge or micrometer. The permissible value is 0.05 mm.

A. Fill in the blanks:

1. The primary purpose of the cooling system in an internal combustion engine is to prevent ______________. 

Ans: Overheating.

2. The cooling system is responsible for removing approximately ______________% of the heat generated during the engine’s power stroke.

Ans: 30%.

3. The radiator is responsible for dissipating heat and cooling down the ______________. 

Ans: Coolant.

4. The component responsible for regulating coolant flow based on engine temperature is called the ______________.

Ans: Thermostat.

B. Multiple Choice Questions:

1. What is the primary function of the cooling system in an internal combustion engine? 

(a) Increase engine efficiency. 

(b) Enhance fuel combustion. 

(c) Prevent overheating. 

(d) Improve exhaust emissions. 

Ans: (c) Prevent overheating. 

2. During which stroke of the internal combustion engine, the highest temperature typically occurs? 

(a) Power stroke. 

(b) Compression stroke. 

(c) Exhaust stroke. 

(d) Intake stroke. 

Ans: (a) Power stroke.

3. What is one of the potential consequences of high engine temperatures? 

(a) Improved fuel efficiency. 

(b) Reduced exhaust emissions. 

(c) Increased lubricant viscosity.

(d) Enhanced engine performance. 

Ans: (c) Increased lubricant viscosity.

4.What is the purpose of the cooling fan in the cooling system? 

(a) Increase engine power. 

(b) Enhance exhaust flow.

(c) Improve fuel combustion. 

(d) Disperse heat and maintain engine temperature. 

Ans: (c) Increased lubricant viscosity.

C. Answer the following questions:

1. Why the cooling system is important in I C Engine? 

Ans: In I.C. engines, during power stroke, the engine temperature reaches between 700-900°C. About 30% heat is released during exhaust stroke. The cooling system removes approximately 30% of the heat. The primary job of the cooling system is to prevent the engine from overheating by transferring this heat to the air. Cooling is necessary because high temperature damages engine components and changes the viscosity of the lubricants. The cooling system protects the engine components by circulating coolant through the passages provided in cylinder block and cylinder head.

2. Name the different component of cooling system. 

Ans: The different components of the cooling system are- Radiator, Thermostat, Water pump, Cooling fan, Coolant passages, Temperature sensor, Radiator cap, Rubber hoses, etc.

3. Name the different methods of engine cooling. 

Ans: The different methods of cooling used in I.C. engines are air cooling, water cooling, oil cooling.

4. Difference between oil cooling system and water-cooling system. 

Ans: Oil cooling system: Uses lubricating oil to absorb and dissipate heat.

Water cooling system: Uses water/coolant circulated through water jackets in the cylinder block/head to absorb and transfer heat to the radiator.

5. What is the function of radiator in cooling system?

Ans: The radiator radiates the heat and cools the coolant.

6. Why coolant is added in the radiator? 

Ans: To maintain optimum temperature and prevent the engine from overheating.

7. What is the function of thermostats?  

Ans: The thermostat regulates the flow of coolant based on the engine temperature.

8. What is the function of water pump and cooling fan? 

Ans: The water pump circulates the coolant through the engine block, cylinder head, radiator and heater core to remove heat from the engine. The cooling fan helps to disperse the heat from the radiator and maintain the engine at the optimum operating temperature.

A. Fill in the blanks:

1. The Multi Point Fuel Injection (MPFI) system is advantageous because it provides a more uniform ________________ to each cylinder, resulting in minimized power differences between cylinders. 

Ans: Air-Fuel Ratio.

2. The Mass Air Flow (MAF) sensor is responsible for monitoring the intake air flow, which is crucial for correcting the Air Flow Map and regulating ________________. 

Ans: EGR Exhaust Gas Recirculation) Flow.

3. The Coolant Temperature Sensor (CTS) is a type of ________________ that changes resistance as the engine’s temperature changes, helping determine the engine’s temperature. 

Ans: Thermistor.

4. The Rail Pressure Sensor (RPS) is located on the fuel common rail and its primary function is to monitor and decide the ________________ of the fuel injector. 

Ans: Injector Energizing Time.

B. Multiple Question Answer:

1. What is the primary advantage of the Multi Point Fuel Injection (MPFI) system over a single-point injection system? 

(a) Improved engine vibration.

(b) Lower fuel consumption.

(c) Increased exhaust emissions.

(d) Enhanced cold start performance. 

Ans: (a) Improved engine vibration.

2. Which component of the MPFI system is responsible for receiving signals from various sensors and sending control signals to actuators? 

(a) Throttle Position Sensor (TPS). 

(b) Crankshaft Position Sensor.

(c) Oxygen (O2) Sensor. 

(d) Engine Control Module (ECM). 

Ans: (d) Engine Control Module (ECM).

3. Which sensor changes resistance based on the temperature of the coolant and helps in regulating engine performance? 

(a) Throttle Position Sensor (TPS). 

(b) Crankshaft Position Sensor. 

(c) Coolant Temperature Sensor (CTS). 

(d) Mass Air Flow (MAF) Sensor.

Ans: (c) Coolant Temperature Sensor (CTS).

4. What is the main function of the EGR Vacuum Modulator in the MPFI system? 

(a) To control exhaust emissions. 

(b) To monitor intake vacuum. 

(c) To regulate fuel pressure. 

(d) To control EGR flow. 

Ans: (d) To control EGR flow.

C. Answer the following questions:

1. What is the full form of MPFI?

Ans: Multi Point Fuel Injection.

2. What are main components of MPFI? 

Ans: The main components of MPFI are listed as:

Sensors, Actuators, and Engine Control Module (ECM).

3. What are the advantages of MPFI over Conventional System? 

Ans: The advantages of MPFI over Conventional System are as under: 

(i) A more uniform Air-Fuel ratio will be supplied to each cylinder, hence the difference in power developed in each cylinder is minimum. Vibration from the engine equipped with this system is less. Due to this, the life of engine components is improved.

(ii) No need to crank the engine twice or thrice in case of cold starting as happens in the carburetor system.

(iii) Immediate response, in case of sudden acceleration / deceleration.

(iv) Since the engine is controlled by ECM (Engine Control Module), more accurate amount of A/F mixture will be supplied and as a result complete combustion will take place. This leads to effective utilization of fuel supplied and hence low emission level. ECM is also known as the computer of the vehicle.

4. What are the disadvantages of MPFI over Conventional System?

Ans: The disadvantages of MPFI over Conventional System are:

(i) The cost of the system is higher than the carburetor system.

(ii) In case of a defect in ECM, the vehicle will not start.

(iii) Difficult to repair and requires trained mechanics.

5. What precaution to be taken while working on MPFI system?

Ans: The precautions that must be taken while working on the MPFI system is that while working on the MPFI system, the battery terminal should be removed first, so that in case of leakage of fuel from injector / fuel rail, fuel may not catch fire.

6. What is Sensor? 

Ans: Sensor is a device which receives input signal and converts it into electrical signal for ECM.

7. What is Actuator? 

Ans: Actuator is a device which receives signals from ECM and converts it into mechanical output.

8. What is ECM? 

Ans: ECM is an Engine Control Module. It is a computer which receives a signal from a sensor, processes it and then sends a control signal to the actuator.

9. Write the two names of sensor used in MPFI. 

Ans: The two names of sensor used in MPFI is:

(i) Crank angle sensor.

(ii) Throttle position sensor.

A. Fill in the blanks:

1. The main purpose of a Common Rail Direct Injection (CRDI) system is to inject fuel directly into the _____________. 

Ans: Cylinder.

2. A turbocharger increases engine power by forcing more _____________ into the combustion chamber. 

Ans: Air.

3. The Electronic Control Module (ECM) is responsible for controlling the _____________ of the diesel engine. 

Ans: Engine Speed.

4. The role of a fuel injector nozzle is to spray fuel into the cylinder in ______________ form for proper combustion. 

Ans: Atomized.

B. Multiple Choice Question:

1. What is the main function of a Common Rail Direct Injection (CRDI) system in a diesel engine? 

(a) Controlling the engine speed. 

(b) Storing fuel.

(c) Filtering air for combustion. 

(d) Injecting fuel into the cylinder. 

Ans: (d) Injecting fuel into the cylinder.

2. What is the purpose of a turbocharger in an engine? 

(a) Increase the size of the engine.  

(b) Improve fuel efficiency. 

(c) Generate electricity. 

(d) Force more air into the combustion chamber.

Ans: (d) Force more air into the combustion chamber.

3. What is the role of the Electronic Control Module (ECM) in a diesel engine’s fuel supply system? 

(a) Filtering the fuel.

(b) Storing excess fuel.

(c) Controlling the engine speed. 

(d) Injecting fuel into the cylinder.

Ans: (c) Controlling the engine speed. 

4. What is the purpose of a fuel injector nozzle in a diesel engine? 

(a) Storing excess fuel. 

(b) Controlling the engine speed. 

(c) Filtering the fuel.

(d) Spraying fuel into the cylinder in an atomized form.

Ans: (d) Spraying fuel into the cylinder in an atomized form.

C. Answer the following questions: 

1. What is the full form of CRDI?

Ans: CRDI (Common Rail Direct Injection); It is a modern technique of fuel supply system used in new generation of diesel engine.

2. What are the main components of CRDI?

Ans: The main components of CRDI are:

(i) Storage of fuel (Fuel tank).

(ii) Filtering of fuel (Fuel filter, sedi meter).

(iii) Delivery of fuel to the injection pump (Primary pump).

(iv) Injecting the fuel into the engine cylinder (rail assembly, unit injector, high pressure pump).

(v) Controlling the engine speed (ECM operated).

3. What are the Advantages of CRDI over Conventional Diesel system?

Ans: The Advantages of CRDI over Conventional Diesel system are:

(i) More power developed.

(ii) Emission level is low.

(iii) Fuel consumption is less.

(iv) Easy cold starting.

4. What are the disadvantages of CRDI over Conventional Diesel system?

Ans: The disadvantages of CRDI over Conventional Diesel system are: 

(i) The cost of a vehicle is more.

(ii) In case of a defect in ECM, the vehicle will not start.

(iii) Difficult to repair and requires trained mechanics.

5. What precaution to be taken while working on CRDI system?

Ans: While working on the CRDI system, the battery terminal should be removed first, so that in case of leakage of fuel from injector / fuel rail, fuel may not catch fire.

6. Explain the use of turbo charger.

Ans: A turbo charger or turbo is a forced induction device used to allow more power to be produced by an engine of a given size. A turbocharged engine can be more powerful and efficient than a naturally aspirated engine because the turbine forces more air (oxygen), and proportionately more fuel, into the combustion chamber than atmospheric pressure alone. Turbo charger is commonly used on truck, car, and bus. Turbo chargers are popularly used with Petrol and Diesel internal combustion engines.

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