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Haryana BSEH Senior Secondary NSQF Automotive study materials
Haryana BSEH Senior Secondary NSQF Automotive study resources

Haryana BSEH Senior Secondary NSQF Automotive practice questions

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Question 1Automotive Workshop Safety, Tools and Equipment

A trainee in an automotive workshop is asked to select the correct fire extinguisher for a small petrol fire near the fuel bench. Which extinguisher class is suitable?

  1. Class B dry powder or foam extinguisher Correct answer.
  2. Class D sodium chloride extinguisher
  3. Class A water extinguisher
  4. Class K wet chemical extinguisher

Explanation

Petrol is a flammable liquid, so it falls in Class B, where dry powder, foam or CO2 extinguishers are used to smother the vapour. Water spreads a burning liquid and can cause the fire to flow and grow. Class D agents are for combustible metals and Class K agents are for cooking oils and fats.

Question 2Automotive Workshop Safety, Tools and Equipment

While grinding a welded bracket on a bench grinder, a technician must protect the eyes. Which item gives the required protection?

  1. Safety goggles or a face shield over goggles Correct answer.
  2. A cloth face mask
  3. Ordinary prescription spectacles
  4. A welding helmet with a dark filter lens

Explanation

Grinding throws high-speed abrasive particles and fragments, so impact-rated safety goggles, or a face shield worn over goggles, are needed. Ordinary spectacles are not impact-rated and leave the sides of the eye open. A dust mask protects the lungs and a welding helmet is for arc radiation, not grinding debris.

Question 3Automotive Workshop Safety, Tools and Equipment

A vehicle is raised on a two-post hoist in the workshop. Which practice is correct before the technician works underneath?

  1. Leave the wheels on the ground and only lift the body
  2. Place the lift pads under the manufacturer's recommended lift points and lock the hoist Correct answer.
  3. Lower the hoist until the vehicle rests on the arms
  4. Support the vehicle by the floor pan under the doors

Explanation

Lift pads must sit at the reinforced lifting points marked by the manufacturer, and the mechanical safety lock must be engaged before anyone goes under the vehicle. Lifting on the floor pan or other weak panels can crush the body and let the vehicle fall. A hoist must never be lowered onto its arms as a way of holding a load.

Question 4Automotive Workshop Safety, Tools and Equipment

Which tool is designed to loosen and tighten a hex-headed bolt without rounding its corners?

  1. A pipe wrench
  2. A pair of locking pliers
  3. A six-point ring spanner of the correct size Correct answer.
  4. An adjustable wrench

Explanation

A six-point ring spanner grips all six flats of the fastener and applies force to the flats rather than the corners, which prevents rounding. Adjustable wrenches and locking pliers grip only part of the head and slip under load. A pipe wrench has serrated jaws intended for round pipe, so it damages bolt heads.

Question 5Automotive Workshop Safety, Tools and Equipment

In a workshop, a hydraulic trolley jack is used to raise one corner of a car for a wheel change. What must be placed under the vehicle before the wheel is removed?

  1. Wooden blocks under the bumper
  2. Rated axle stands at the recommended support points Correct answer.
  3. A second trolley jack at the same corner
  4. Nothing, because the jack holds the load

Explanation

A trolley jack is a lifting device only and may creep down under load, so rated axle stands must carry the vehicle before any work is done. Stands are placed at the manufacturer's support points so the load is carried by strong structural sections. Bumper or plastic trim cannot support the vehicle weight.

Question 6Automotive Workshop Safety, Tools and Equipment

Which property makes a torque wrench different from an ordinary socket handle?

  1. It multiplies force so less effort is needed
  2. It releases or signals at a preset torque so fasteners are tightened accurately Correct answer.
  3. It can be extended with a pipe for extra leverage
  4. It can be used as a breaker bar for loosening

Explanation

A torque wrench is a measuring instrument that indicates or releases at a set torque, giving accurate and repeatable clamping load. Using it to loosen fasteners or extending it with a pipe overloads the spring or beam and destroys its calibration. It is not a force multiplier.

Question 7Automotive Workshop Safety, Tools and Equipment

A technician must store a set of files and chisels after use. Which practice protects the tools and the next user?

  1. Leave the chisel edge facing outward in an open tray
  2. Oil the file teeth to stop rust and stack the chisels together
  3. Store them loose in a drawer with other tools
  4. Fit handles to files and chisels and store them in a rack or roll, edges away from the body Correct answer.

Explanation

Files and chisels need sound handles, and chisels must never be struck or carried without one. Storing them in a rack or tool roll keeps cutting edges protected and prevents contact injuries. Oiling file teeth would clog the cut and reduce its cutting action.

Question 8Automotive Workshop Safety, Tools and Equipment

An air impact wrench is being used to remove wheel nuts. Which precaution applies to the compressed air hose?

  1. Use any hose available, since pressure is low
  2. Check the hose and couplings for damage and secure them with a whip check or safety clip Correct answer.
  3. Disconnect the tool by pulling on the hose
  4. Coil the hose tightly around the operator's arm

Explanation

A pressurised air hose that whips free can cause severe injury, so hoses and couplings must be inspected and secured with a whip check or retaining clip. Pulling a tool by its hose damages the coupling and can release it under pressure. Hoses must never be wrapped around the body.

Question 9Automotive Workshop Safety, Tools and Equipment

A battery is being removed from a vehicle before welding work on the body. What is the correct order of disconnection and the reason for it?

  1. Disconnect the negative terminal first to avoid a short through the spanner to the body Correct answer.
  2. Disconnect the positive terminal first to break the circuit quickly
  3. Leave the battery connected but switch off the ignition
  4. Disconnect both terminals together with a double spanner

Explanation

The negative terminal is connected to the vehicle body, so removing it first means a spanner touching the body creates no circuit. If the positive is loosened first, a spanner bridging it to the body causes a heavy short circuit and possible explosion. The battery must be fully isolated before welding to protect electronic units.

Question 10Automotive Workshop Safety, Tools and Equipment

A technician is preparing to weld a sill panel on a vehicle with an electronic control unit. Which precaution protects the electronics?

  1. Weld with the battery connected to keep the ECU powered
  2. Increase welding current to finish quickly
  3. Disconnect the battery and unplug the ECU, and clamp the earth close to the weld Correct answer.
  4. Attach the earth clamp to the rear bumper

Explanation

Isolating the battery and unplugging the ECU removes the path for stray welding current, and a close earth clamp keeps the return path short. High current and a distant earth point force current through wiring and bearings. Leaving the battery connected exposes the electronics to voltage spikes.

Question 11Automotive Workshop Safety, Tools and Equipment

In a workshop with a hydraulic press, the operator notices the pressure gauge reading rising while the workpiece does not move. What is the correct action?

  1. Continue pressing until the workpiece yields
  2. Release the pressure and check the setup, since the load path is blocked or misaligned Correct answer.
  3. Tap the workpiece with a hammer while pressure is held
  4. Stand closer to watch the ram more carefully

Explanation

A blocked or misaligned load path can cause the workpiece or press components to slip or shatter suddenly under stored energy. Pressure must be released before the setup is inspected and corrected. Standing close or striking the workpiece under load exposes the operator to flying fragments.

Question 12Automotive Workshop Safety, Tools and Equipment

Which practice is correct when using a bench grinder fitted with a wire brush wheel?

  1. Wear loose gloves and a long-sleeved shirt without cuffs fastened
  2. Grind on the side of the wheel for better reach
  3. Remove the tool rest to give more clearance
  4. Wear close-fitting sleeves, eye protection and hold the work firmly against the wheel's lower quadrant Correct answer.

Explanation

Loose clothing or gloves can be caught by a rotating wire wheel and drag the hand in, so sleeves must be close-fitting and eye protection worn against flying wires. Work is held against the lower part of the wheel so it is pushed down onto the rest. The tool rest and guard must stay in place.

Question 13Automotive Workshop Safety, Tools and Equipment

A vehicle with a suspected fuel leak is brought into the workshop. Which sequence best controls the risk before diagnosis begins?

  1. Ventilate the area, remove ignition sources, place a drip tray and absorbent, then isolate the battery Correct answer.
  2. Wipe the spill with a dry cloth and continue work
  3. Start the engine to locate the leak by sound
  4. Use a flame to check whether the vapour burns

Explanation

Fuel vapour is heavier than air and ignites easily, so ventilation, removal of ignition sources and containment of the spill come first, followed by battery isolation to prevent sparks. Dry wiping spreads the fuel and generates static. A flame test is extremely dangerous and never acceptable.

Question 14Automotive Workshop Safety, Tools and Equipment

When charging a lead-acid battery in the workshop, which precaution applies to the charging area?

  1. Seal the battery in a closed box during charging
  2. Charge at the highest available current to save time
  3. Charge with the caps removed and a cigarette nearby to check ventilation
  4. Charge in a well-ventilated area away from sparks and flames, with the caps in place Correct answer.

Explanation

Lead-acid charging releases hydrogen, which forms an explosive mixture with air, so ventilation and removal of ignition sources are essential. Caps are left in place on maintenance-free types and loosened only as the manufacturer directs, and the area must be spark-free. Excessive current overheats the battery and shortens its life.

Question 15Automotive Workshop Safety, Tools and Equipment

A technician is about to use a hydraulic floor jack that has a small oil weep at the ram seal. What is the correct decision?

  1. Use it, since a small leak does not affect lifting
  2. Tag it out of service and have the seal repaired before use Correct answer.
  3. Use it only for light vehicles to reduce the load
  4. Top up the reservoir and continue using it

Explanation

A leaking ram seal means the jack can lose pressure and lower the load without warning, so it must be withdrawn from service and repaired. Topping up the oil does not fix the seal and may hide the fault. Restricting use to light vehicles still leaves an uncontrolled lowering risk.

Question 16Automotive Workshop Safety, Tools and Equipment

Which measuring instrument is most suitable for checking the outside diameter of a valve stem to an accuracy of 0.01 mm?

  1. A dial test indicator on a magnetic base
  2. A feeler gauge
  3. A vernier caliper or a micrometer Correct answer.
  4. A steel rule

Explanation

A micrometer reading to 0.01 mm, or a vernier caliper of similar resolution, is used for external diameters on small cylindrical parts such as valve stems. A steel rule reads only to about 0.5 mm, a feeler gauge measures gaps, and a dial test indicator is used for runout and alignment rather than diameter.

Question 17Automotive Workshop Safety, Tools and Equipment

A micrometer is left closed on its anvil overnight after use. What is the likely effect on the instrument?

  1. The frame becomes magnetised and reads high
  2. The ratchet becomes more accurate
  3. The measuring faces are stressed and the zero may shift, so readings become unreliable Correct answer.
  4. The thimble graduations become clearer

Explanation

Leaving a micrometer closed keeps the spindle under load on the anvil, which can deform the measuring faces or alter the zero setting. It should be opened a little and stored in its case after use. Magnetism is not caused by closing the instrument, and no part becomes more accurate through misuse.

Question 18Automotive Workshop Safety, Tools and Equipment

A four-post hoist is used for wheel alignment work. Which check should be made before the vehicle is driven onto it?

  1. Raise the hoist halfway to save time later
  2. Confirm the hoist is fully lowered, level and the runways are clear Correct answer.
  3. Leave the safety locks disengaged for faster operation
  4. Check only that the vehicle engine starts

Explanation

A drive-on hoist must be fully down and level so the wheels roll onto the runways without a step, and the runways must be clear of tools and obstructions. Raising it part way or leaving the locks disengaged creates a fall or trip hazard. Engine condition has no bearing on safe loading.

Question 19Automotive Workshop Safety, Tools and Equipment

A workshop stores oxygen and acetylene cylinders for gas welding. Which arrangement is correct?

  1. Store oxygen and fuel gas cylinders separately, upright and secured, with flashback arrestors fitted to the torch lines Correct answer.
  2. Keep cylinders unsecured so they can be moved quickly
  3. Store acetylene next to a grinding area to save space
  4. Store both cylinders lying together in a locked cupboard

Explanation

Fuel gas and oxygen must be stored apart, upright and restrained so they cannot fall, and flashback arrestors on the lines prevent a flame travelling back into the cylinder. Storing them together or near hot work increases the risk of a combined fire or explosion. Unsecured cylinders can topple and shear the valve.

Question 20Automotive Workshop Safety, Tools and Equipment

A socket used on an impact wrench repeatedly splits at the drive end. Which explanation is most likely?

  1. The fastener is made of aluminium
  2. The extension bar is too long
  3. The socket is too hard for the fastener
  4. The socket is a chrome vanadium hand-tool type rather than an impact-rated type Correct answer.

Explanation

Impact wrenches deliver repeated shock loads, so sockets must be impact-rated, usually chrome molybdenum and marked as such. Standard chrome vanadium hand sockets are harder and more brittle, so they crack or shatter under impact. Extension length and fastener material do not cause this failure pattern.

Question 21Automotive Workshop Safety, Tools and Equipment

A vehicle is to be raised on a single-post or scissor lift with a low ceiling above it. Which control measure is most important?

  1. Check the maximum lift height against the ceiling clearance and fit a height limiter Correct answer.
  2. Ask a colleague to watch and shout if contact occurs
  3. Remove the overhead light fittings to gain space
  4. Increase hydraulic pressure to lift faster

Explanation

The lift travel must be limited so the vehicle roof cannot strike the ceiling or overhead equipment, which means checking clearance and fitting a height limiter. Raising pressure or relying on a spotter does not remove the hazard. Removing light fittings creates an electrical hazard and darkness.

Question 22Automotive Workshop Safety, Tools and Equipment

Which statement correctly describes the purpose of a fume extraction system at an MIG welding bay?

  1. It supplies shielding gas to the torch
  2. It increases the welding current for deeper penetration
  3. It removes welding fume from the breathing zone before the operator inhales it Correct answer.
  4. It cools the weld to reduce distortion

Explanation

Welding fume contains metal oxides and gases that damage the respiratory system, so extraction captures it at or near the arc before it reaches the breathing zone. Shielding gas is supplied through the torch, and current is set on the machine. Cooling the weld is not the function of extraction and would harm weld quality.

Question 23Automotive Workshop Safety, Tools and Equipment

A technician must choose between a compression tester and a cylinder leakage tester for diagnosing a suspected burnt exhaust valve. Which reasoning is correct?

  1. Both instruments measure oil pressure, so either will do
  2. The compression tester measures leak-down rate directly, so it is the only choice
  3. The leakage tester supplies air to the cylinder and shows where it escapes, so it can identify a leaking valve by air heard at the intake or exhaust Correct answer.
  4. The leakage tester measures battery voltage during cranking

Explanation

A cylinder leakage tester feeds regulated air into a cylinder at TDC and the percentage loss plus the escape point indicate the faulty component; air heard at the exhaust points to an exhaust valve. A compression tester shows that compression is low but not where it is lost. Neither instrument measures oil pressure or battery voltage.

Question 24Automotive Workshop Safety, Tools and Equipment

During a road test, a technician hears a rhythmic knock from an engine that changes with load. Which workshop practice best supports an accurate diagnosis?

  1. Hold the throttle open by hand while standing in front of the vehicle
  2. Rev the engine to maximum speed in the bay with the bonnet closed
  3. Ignore the noise until a fault code appears
  4. Use a stethoscope or listening probe at the suspected area with the vehicle securely chocked and in neutral Correct answer.

Explanation

A listening probe localises the noise, and chocking the vehicle with the transmission in neutral keeps it stationary and safe during the test. Revving to maximum in an enclosed bay is noisy and dangerous, and standing in front of the vehicle puts the technician in the path of the vehicle. Waiting for a fault code may never identify a mechanical knock.

Question 25Automotive Engine Systems and Overhaul

While overhauling a four-stroke petrol engine, a technician measures the cylinder bore and finds it is 0.12 mm larger than the standard size and slightly oval. Which workshop action is the correct next step?

  1. Fit new standard rings and accept the ovality as normal wear
  2. Rebore to the next oversize and fit matching oversize pistons and rings Correct answer.
  3. Hone the bore lightly and refit the original standard pistons
  4. Replace only the piston rings with a thicker oil-control ring

Explanation

When bore wear or ovality exceeds the manufacturer's service limit, the bore must be refinished to the next oversize and matched with oversize pistons and rings so the correct piston-to-bore clearance is restored. Light honing only restores surface finish and cannot correct a worn or oval bore. Simply fitting standard rings leaves excessive clearance and poor sealing.

Question 26Automotive Engine Systems and Overhaul

The piston-to-bore clearance of an engine is specified as 0.030 to 0.050 mm. A technician measures the clearance with a feeler gauge and obtains 0.065 mm. What does this measurement indicate?

  1. The clearance exceeds the maximum and piston slap or oil consumption may occur Correct answer.
  2. The clearance is below the minimum and the piston may seize
  3. The clearance is within the specified service range
  4. The measurement is invalid because clearance cannot be checked with a feeler gauge

Explanation

The measured value of 0.065 mm is larger than the upper limit of 0.050 mm, so the assembly is out of specification on the loose side. Excessive clearance allows the piston to rock in the bore, producing slap noise, poor ring sealing and increased oil consumption. The correct remedy is to check piston and bore sizes and replace or recondition as required.

Question 27Automotive Engine Systems and Overhaul

In a four-cylinder engine, the firing order is 1-3-4-2. If cylinder 1 is on its compression stroke, which cylinder is on the power stroke at that instant in a correctly timed engine?

  1. Cylinder 2
  2. Cylinder 4
  3. Cylinder 3 Correct answer.
  4. No cylinder, because all others are on intake

Explanation

In a four-stroke cycle each cylinder is 180 degrees of crankshaft rotation behind the previous one in the firing order. With firing order 1-3-4-2 and cylinder 1 at compression, the cylinder that fired one stroke earlier, cylinder 3, is now on its power stroke. Cylinder 4 is on intake and cylinder 2 is on exhaust.

Question 28Automotive Engine Systems and Overhaul

A valve clearance check on a cold engine shows the exhaust valve clearance is below the manufacturer's minimum. What is the most likely consequence if the engine is run in this condition?

  1. The valve will open too early and the engine will idle faster
  2. The valve will open too late and engine power will increase
  3. The valve will not close fully, causing compression loss and possible burning Correct answer.
  4. The valve will close too early and produce a loud tapping noise

Explanation

Insufficient exhaust valve clearance means the valve is held slightly off its seat when the engine is hot, so it cannot seal or shed heat to the cylinder head. The result is compression loss, misfiring and a risk of burning the valve face. Clearance must be adjusted to specification with the engine cold as stated by the maker.

Question 29Automotive Engine Systems and Overhaul

Which component in a pressurised engine lubrication system directly limits the maximum oil pressure in the galleries?

  1. Pressure relief valve Correct answer.
  2. Oil strainer in the sump
  3. Oil filter bypass valve
  4. Oil pump drive gear

Explanation

The pressure relief valve opens when gallery pressure reaches its setting and diverts excess oil back to the sump or inlet side, capping the maximum pressure. The filter bypass valve protects flow when the filter is blocked, and the strainer only stops large debris. The pump gear simply generates flow.

Question 30Automotive Engine Systems and Overhaul

An engine is reported to crank but not start, and a compression test gives about 6 bar on all cylinders against a specified minimum of 10 bar. Which cause best fits these readings?

  1. A faulty coolant temperature sensor
  2. A clogged fuel injector
  3. A weak ignition coil
  4. Worn piston rings and cylinder bores Correct answer.

Explanation

Uniformly low compression across all cylinders points to a mechanical sealing problem common to all cylinders, such as worn rings, glazed or worn bores or leaking head gasket. Ignition, fuel and sensor faults affect combustion but do not reduce cranking compression. A wet test would normally raise the reading if the rings are the cause.

Question 31Automotive Engine Systems and Overhaul

During a cylinder leakage test, air escapes continuously through the radiator filler neck with bubbles visible. Which defect does this indicate?

  1. Blown head gasket or cracked head between combustion chamber and water jacket Correct answer.
  2. Leaking exhaust valve
  3. Worn piston rings
  4. Leaking intake valve

Explanation

Air appearing in the cooling system during a leakage test shows a path from the combustion chamber into the water jacket, typically a failed head gasket or a cracked cylinder head. Leaking intake or exhaust valves would show air at the throttle body or tailpipe respectively. Worn rings would show air at the crankcase breather.

Question 32Automotive Engine Systems and Overhaul

In a diesel engine overhaul, the function of the turbocharger wastegate is to:

  1. Prevent oil from entering the compressor housing
  2. Limit boost pressure by bypassing exhaust gas around the turbine Correct answer.
  3. Increase fuel delivery as boost rises
  4. Cool the compressed intake air before it enters the manifold

Explanation

The wastegate is a valve that opens to divert exhaust gas around the turbine once the preset boost pressure is reached, limiting turbine speed and manifold pressure. Charge cooling is the job of the intercooler, and fuel enrichment is handled by the injection pump or ECU. Oil sealing is provided by the turbocharger seals.

Question 33Automotive Engine Systems and Overhaul

Which statement correctly describes the purpose of deglazing and cross-hatch honing of a cylinder bore before fitting new rings?

  1. It increases the bore diameter to the next oversize
  2. It hardens the bore surface to reduce wear
  3. It removes distortion caused by head bolt tightening
  4. It creates a surface pattern that helps new rings bed in and retain oil Correct answer.

Explanation

Honing produces a fine cross-hatch pattern that provides controlled roughness for ring seating while holding oil for lubrication. It does not change bore size to an oversize, correct distortion or harden the surface. Bore size changes require boring or reboring.

Question 34Automotive Engine Systems and Overhaul

A technician is checking valve spring free length during an overhaul and finds one spring is 3 mm shorter than the specification. What is the correct action?

  1. Fit the spring as it is because length does not affect valve operation
  2. Add a spacer washer under the spring to restore its length
  3. Replace the spring because a shortened spring gives reduced seat pressure Correct answer.
  4. Cut the other springs to match the short one

Explanation

A spring that has lost free length has also lost its fitted load, so valve seating and control at high speed are compromised. The correct repair is replacement with a spring within specification. Spacers and matching shortened springs are not acceptable workshop practice.

Question 35Automotive Engine Systems and Overhaul

Which of these is the primary function of the thermostat in an engine cooling system?

  1. To cool the coolant before it returns to the engine
  2. To release excess pressure from the cooling system
  3. To circulate coolant through the radiator
  4. To maintain the engine coolant within its designed operating temperature range Correct answer.

Explanation

The thermostat opens and closes with temperature to control coolant flow to the radiator, keeping the engine near its designed operating temperature. Circulation is provided by the water pump, pressure is regulated by the radiator cap and heat is removed by the radiator itself.

Question 36Automotive Engine Systems and Overhaul

After assembling an engine, a technician must set the valve timing. Which reference marks should be aligned to ensure correct timing?

  1. The crankshaft pulley TDC mark with the camshaft sprocket timing marks Correct answer.
  2. The flywheel ring gear mark with the starter pinion
  3. The water pump pulley mark with the alternator belt mark
  4. The oil pump drive mark with the distributor rotor

Explanation

Valve timing is established by aligning the crankshaft at top dead centre with the camshaft timing marks, so the camshaft position relative to the crank is fixed. The other pairs listed do not control valve timing. Incorrect alignment can cause piston-to-valve contact.

Question 37Automotive Engine Systems and Overhaul

What is the main reason for torqueing cylinder head bolts in a specified sequence and in stages?

  1. To ensure even clamping and prevent head distortion or gasket failure Correct answer.
  2. To stretch the bolts so they cannot loosen
  3. To reduce the time needed for assembly
  4. To compress the gasket to zero thickness

Explanation

Staged, sequenced torqueing spreads the clamping load gradually so the head seats evenly on the block and the gasket seals without distortion. It is not primarily a time-saving measure, and the gasket must retain a designed thickness. Torque-to-yield bolts are a design feature, not the aim of the sequence.

Question 38Automotive Engine Systems and Overhaul

A diesel engine shows low power, black exhaust smoke and a knocking sound under load. A compression test is normal and the air filter is clean. Which area should be checked next?

  1. The fuel injection quantity and injector spray pattern Correct answer.
  2. The valve stem oil seals
  3. The radiator cap pressure rating
  4. The spark plug gap

Explanation

Black smoke with knocking under load in a diesel points to over-fuelling or poor atomisation, so injection quantity and spray pattern are the next checks. Compression is already confirmed normal and the air supply is clean. Spark plugs do not exist on a diesel, and the other items do not cause these symptoms.

Question 39Automotive Engine Systems and Overhaul

Which measurement tool is most appropriate for checking the out-of-roundness of a cylinder bore accurately?

  1. Steel rule
  2. Feeler gauge
  3. Bore gauge or inside micrometer Correct answer.
  4. Vernier caliper

Explanation

A bore gauge or inside micrometer reads internal diameter to fine increments at different heights and directions, allowing taper and ovality to be calculated. A vernier caliper is too coarse for this precision, a steel rule is unsuitable and a feeler gauge measures gaps, not bores.

Question 40Automotive Engine Systems and Overhaul

In a multi-cylinder engine, what is the main purpose of the crankshaft counterweights?

  1. To increase the engine's compression ratio
  2. To hold the flywheel in position
  3. To drive the oil pump
  4. To balance the rotating assembly and reduce bearing loads from inertia forces Correct answer.

Explanation

Counterweights offset the mass of the crank throws and connecting rods, reducing vibration and the load on main bearings from inertia forces. They do not affect compression ratio, drive the oil pump or fix the flywheel. Balancing the rotating assembly is essential for smooth, durable operation.

Question 41Automotive Engine Systems and Overhaul

During engine assembly, plastigauge is used to check which of the following?

  1. Cylinder head flatness
  2. Piston ring end gap
  3. Valve stem-to-guide clearance
  4. Connecting rod and main bearing oil clearance Correct answer.

Explanation

Plastigauge is a crushable plastic strip placed between the bearing shell and journal; its flattened width read against a scale gives the bearing oil clearance. Ring end gap is checked with a feeler gauge in the bore, guide clearance with a dial gauge or bore gauge and head flatness with a straight edge and feeler gauge.

Question 42Automotive Engine Systems and Overhaul

A petrol engine has a misfire that moves from cylinder to cylinder when the ignition coils are swapped. Which conclusion is most reasonable?

  1. The fault follows the coil, indicating a defective coil Correct answer.
  2. The fault is due to incorrect valve clearance
  3. The fault is caused by low fuel pressure
  4. The fault is in a cylinder-specific mechanical component

Explanation

If the misfire moves with the coil to another cylinder, the coil is the common factor and is therefore faulty. A mechanical or injector fault would stay with its original cylinder. Fuel pressure and valve clearance faults would not follow a swapped coil.

Question 43Automotive Engine Systems and Overhaul

Which of the following best explains why piston rings are fitted with their end gaps staggered around the piston?

  1. To reduce the total ring tension on the bore
  2. To make ring installation quicker
  3. To prevent the gaps lining up and creating a direct path for blow-by Correct answer.
  4. To allow oil to drain from the ring grooves

Explanation

Staggering the end gaps means combustion gas cannot pass straight through aligned gaps into the crankcase, which would increase blow-by and reduce compression. Ring tension is set by ring design, installation speed is irrelevant and oil drainage is handled by the oil ring and drain holes.

Question 44Automotive Engine Systems and Overhaul

An engine's camshaft is chain driven and the chain has excessive slack. What is the most likely effect on engine operation?

  1. Increased coolant temperature only
  2. Higher oil pressure in the galleries
  3. Incorrect valve timing and possible piston-to-valve contact Correct answer.
  4. A louder exhaust note with no other effect

Explanation

Excess chain slack allows the camshaft to lag the crankshaft, upsetting valve timing and, in severe cases, allowing valves and pistons to collide. Oil pressure and coolant temperature are unrelated to cam chain slack. The correct repair is replacement of the chain and tensioner.

Question 45Automotive Engine Systems and Overhaul

A technician is checking the flatness of a cylinder head with a straight edge and feeler gauge. The maximum permissible warpage is 0.05 mm. A 0.10 mm feeler gauge slides under the straight edge at the centre. What is the correct interpretation?

  1. The head is warped beyond limits and must be resurfaced or replaced Correct answer.
  2. The measurement is wrong because feeler gauges cannot check flatness
  3. The head is within limits and can be refitted
  4. The head is cracked and must be scrapped

Explanation

A 0.10 mm gap exceeds the 0.05 mm limit, so the head is warped beyond specification and needs resurfacing within the maker's allowance or replacement. Flatness is commonly checked this way. Warpage is not the same as a crack, which requires a separate crack test.

Question 46Automotive Engine Systems and Overhaul

Which statement about the operation of a four-stroke spark-ignition engine is correct?

  1. The piston moves from bottom dead centre to top dead centre during intake
  2. The exhaust valve opens at the start of the intake stroke
  3. The intake valve closes during the power stroke
  4. The spark occurs near the end of the compression stroke Correct answer.

Explanation

Ignition is timed to occur just before the end of compression, close to top dead centre, so the burning charge pushes the piston down on the power stroke. The intake valve closes at the end of intake, the exhaust valve opens near the end of the power stroke, and the piston travels downward from top to bottom during intake.

Question 47Automotive Engine Systems and Overhaul

An engine has been rebuilt and the oil pressure warning lamp stays on at idle. Which cause should be checked first?

  1. Drive belt tension on the alternator
  2. Oil level, oil grade and the oil pressure switch circuit Correct answer.
  3. Spark plug heat range
  4. Radiator fan operation

Explanation

Low oil pressure indication is first checked by confirming correct oil level and viscosity and verifying that the switch and wiring are not giving a false warning. Only then are the pump, relief valve and bearing clearances investigated. The other items have no bearing on oil pressure.

Question 48Automotive Engine Systems and Overhaul

During a compression test, adding a small quantity of engine oil to a cylinder raises its reading noticeably. What does this indicate?

  1. Worn piston rings or cylinder bore Correct answer.
  2. A blown head gasket
  3. A leaking exhaust valve
  4. Incorrect ignition timing

Explanation

Oil temporarily seals the gap between rings and bore, so a rise in compression after the wet test points to ring or bore wear. A leaking valve or head gasket would not be sealed by oil in this way. Ignition timing does not change cranking compression.

Question 49Automotive Engine Systems and Overhaul

A technician compares two identical engines: one uses a longer duration camshaft with more valve overlap, the other uses a standard camshaft. Which statement best predicts the difference in behaviour?

  1. The long-duration cam gives smoother idle and higher low-speed torque
  2. The long-duration cam lowers compression pressure at all engine speeds
  3. Both camshafts give identical torque curves at all speeds
  4. The long-duration cam improves high-speed breathing but reduces low-speed torque and idle quality Correct answer.

Explanation

More duration and overlap improve cylinder filling at high speed but reduce low-speed trapping efficiency, causing rougher idle and less torque at low rpm. The two cams cannot give identical curves, and compression pressure is only lowered at low speeds where overlap has most effect. Camshaft selection is a compromise between these characteristics.

Question 50Automotive Engine Systems and Overhaul

During a full engine overhaul, a technician measures the crankshaft main journal diameters and finds they are within the wear limit but show a taper of 0.03 mm. Which component clearance is most directly affected by journal taper, and what is the standard remedy?

  1. Valve guide clearance; ream the guides to the next size
  2. Main bearing oil clearance; regrind the journal to the next undersize and fit matching bearings Correct answer.
  3. Piston-to-bore clearance; fit oversize pistons
  4. Big-end bearing clearance; replace the connecting rods

Explanation

Main journal taper means the journal diameter varies along its length, so the oil clearance in the main bearing changes as the shaft rotates, which can cause uneven oil wedge formation and bearing knock. The accepted workshop remedy is to grind the journal to a uniform undersize and fit bearings of the corresponding undersize grade. Piston and valve guide clearances are set by other components and are not corrected by journal grinding.