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Odisha CHSE VOC-ITV Four Wheeler Service Technician study materials
Odisha CHSE VOC-ITV Four Wheeler Service Technician study resources

Odisha CHSE VOC-ITV Four Wheeler Service Technician practice questions

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Question 1Workshop safety, tools and equipment

A trainee is about to sharpen a chisel on the bench grinder in the four-wheeler workshop. Which item of personal protective equipment is essential to guard the eyes against flying abrasive particles?

  1. A rubber apron
  2. Cotton hand gloves
  3. Safety goggles fitted with side shields Correct answer.
  4. A disposable dust mask

Explanation

A bench grinder throws hard abrasive grit and metal fragments at high speed, so impact-resistant eye protection that seals around the eyes is required. Goggles with side shields prevent particles from entering from the side as well as the front. A face shield may be worn over goggles for heavy grinding, but it does not replace them.

Question 2Workshop safety, tools and equipment

A car is to be raised at the front with a hydraulic trolley jack for an oil change. What must be placed behind the rear wheels before the jack is operated?

  1. A second trolley jack under the rear bumper
  2. Wheel chocks against the rear tyres Correct answer.
  3. Two axle stands under the rear axle
  4. Wooden blocks under the trolley jack wheels

Explanation

Wheel chocks are placed against the wheels that remain on the floor to stop the vehicle rolling while the other end is lifted. They must be fitted before the jack takes the weight and must remain in place until the vehicle is lowered again. Axle stands are used to support the raised vehicle, not to chock the wheels still on the ground.

Question 3Workshop safety, tools and equipment

Petrol spilled during a fuel-filter change ignites on the workshop floor. In the fire classification used for workshop extinguisher selection, which class is this fire?

  1. Class A
  2. Class D
  3. Class C
  4. Class B Correct answer.

Explanation

Class B fires involve flammable liquids such as petrol, diesel, paint thinner and lubricating oil. They are normally tackled with foam, dry powder or carbon dioxide extinguishers, never with a plain water jet. Class A covers solid combustibles, Class C flammable gases and Class D combustible metals.

Question 4Workshop safety, tools and equipment

A technician uses a click-type torque wrench with a breaker bar attached to loosen a seized wheel nut. Why is this practice unacceptable in a four-wheeler workshop?

  1. The nut will be tightened instead of loosened
  2. The socket will not fit the wheel nut
  3. The wrench will apply too little torque
  4. The wrench is a measuring instrument and may lose calibration or break Correct answer.

Explanation

A torque wrench is a calibrated measuring instrument designed for controlled tightening, not for breaking loose seized fasteners. The shock load from loosening can damage the internal mechanism and leave the wrench out of calibration. A breaker bar or impact wrench of the correct size should be used to loosen the nut first.

Question 5Workshop safety, tools and equipment

After raising a vehicle with a trolley jack, where should the axle stands be placed before any work is done underneath?

  1. Under the floor pan at the centre of the passenger compartment
  2. Under the plastic sill trim
  3. Under the brake disc or suspension arm ball joint
  4. Under the manufacturer's reinforced jacking points or axle beams Correct answer.

Explanation

Axle stands must bear on strong structural points that the vehicle manufacturer identifies for jacking and supporting. Reinforced jacking points and axle beams are designed to carry the vehicle weight without crushing. The vehicle should be lowered gently onto the stands and given a stability check before anyone goes underneath.

Question 6Workshop safety, tools and equipment

A technician wants to clean brake dust from his overalls with the workshop compressed-air gun. What is the correct safety instruction?

  1. Use compressed air after applying barrier cream to the skin
  2. Use the air gun at full pressure but keep the nozzle 300 mm away
  3. Use compressed air only if safety goggles are worn
  4. Never use compressed air on the body; use a vacuum or brush and wear a dust mask Correct answer.

Explanation

Compressed air can drive brake dust and other particles into the eyes and skin, and in severe cases can force air into the tissues. Brake dust is also a respiratory hazard, so a vacuum or soft brush with a dust mask is the correct method. Compressed air should be used for cleaning components and parts, not clothing or skin.

Question 7Workshop safety, tools and equipment

A flooded lead-acid battery with removable vent caps is being charged in the workshop. Why should the vent caps be kept loose or removed and the area ventilated?

  1. To make it easier to check the specific gravity
  2. To let the electrolyte cool faster
  3. To allow acid to drain out of the cells
  4. To allow hydrogen gas to escape and prevent an explosive mixture Correct answer.

Explanation

Charging a lead-acid battery produces hydrogen gas, which can form an explosive mixture with air in a closed space. Loose or removed vent caps allow the gas to escape, and ventilation keeps the concentration below the explosive limit. All flames, sparks and smoking materials must be kept away from the charging area.

Question 8Workshop safety, tools and equipment

A technician removes the guard from a 100 mm angle grinder so that it will fit inside a tight wheel arch. What is the main additional hazard created by this action?

  1. The disc will run at a lower speed
  2. A bursting disc or its fragments can strike the operator Correct answer.
  3. The tool will produce more vibration in the hand
  4. The grinder motor will overheat and catch fire

Explanation

The guard is designed to contain fragments if the abrasive disc bursts or a piece breaks away at high speed. Removing it exposes the operator and nearby workers to flying debris and direct contact with the spinning disc. The correct practice is to use a smaller grinder or a different tool rather than to remove the guard.

Question 9Workshop safety, tools and equipment

A front-wheel-drive car is on a two-post lift. Before the technician goes under it, what is the correct final step after the lifting arms have contacted the vehicle?

  1. Place axle stands under the lift arms and leave the lift in the air
  2. Raise fully and rely on the hydraulic pressure to hold the vehicle
  3. Leave one arm slightly lower so that the vehicle tilts towards the technician
  4. Raise until the wheels clear the floor, check stability, then lower onto the mechanical safety locks Correct answer.

Explanation

A two-post lift must be lowered onto its mechanical safety locks before anyone works underneath. The vehicle should first be raised only until the wheels clear the floor so that its stability on the arms can be checked. Hydraulic pressure alone is not an acceptable support because a hose or valve failure can drop the vehicle.

Question 10Workshop safety, tools and equipment

A torque wrench is fitted with a crowfoot wrench set at exactly 90 degrees to the handle to reach a recessed suspension bolt. The wrench is set to 90 N·m. What torque is applied to the bolt, assuming the crowfoot is at 90 degrees?

  1. More than 90 N·m because the crowfoot lengthens the lever
  2. Approximately 90 N·m because the effective lever length is unchanged Correct answer.
  3. Less than 90 N·m because the crowfoot absorbs torque
  4. Zero, because a crowfoot cannot be used with a torque wrench

Explanation

When a crowfoot is at 90 degrees to the torque wrench handle, the perpendicular distance from the handle to the fastener is unchanged, so the set torque is still approximately correct. At other angles the effective lever length changes and a correction calculation is needed. The 90-degree position is therefore the preferred way to use an offset adapter.

Question 11Workshop safety, tools and equipment

A technician is removing a seized wheel nut with a pneumatic impact wrench in the four-wheeler workshop. Which socket should be selected for this operation?

  1. A thin-walled deep socket with a chrome finish
  2. A universal-joint socket with a chrome finish
  3. A black, thick-walled impact socket Correct answer.
  4. A chrome-plated socket from the hand-tool set

Explanation

Impact sockets are made from malleable steel and have thicker walls than hand sockets, so they absorb the repeated shock loads of an impact wrench without cracking. A chrome-plated hand socket is hardened and brittle; under impact it can shatter and throw metal fragments. For wheel nuts and other high-torque fasteners, the socket must be matched to the tool.

Question 12Workshop safety, tools and equipment

Engine oil spills onto the workshop floor during an oil change on a four-wheeler. What is the correct immediate action?

  1. Wipe it with a petrol-soaked rag and put the rag in the general bin
  2. Cover the spill with absorbent granules, sweep it up, and dispose of it as hazardous waste Correct answer.
  3. Wash the oil into the floor drain with water
  4. Leave it to dry and place a warning cone over it

Explanation

Oil is a hazardous waste and must not enter drains or soil. Absorbent granules or pads soak it up so it can be swept and disposed of through the workshop's hazardous-waste route. Leaving oil on the floor creates a slip hazard and pollutes the workshop.

Question 13Workshop safety, tools and equipment

A new 200 mm grinding wheel is to be fitted to a bench grinder. Before mounting, the technician taps the wheel lightly with a screwdriver handle and listens to the sound. What does a dull thud indicate?

  1. The wheel's abrasive grade is too coarse for the application
  2. The wheel is correctly balanced and safe to mount
  3. The wheel is too new and needs a low-speed run-in
  4. The wheel has a crack or internal damage and must be discarded Correct answer.

Explanation

The ring test checks a grinding wheel for internal cracks before it is mounted. A sound wheel gives a clear metallic ring when tapped lightly, while a dull thud suggests a crack or delamination. A damaged wheel can burst at operating speed, so it must be discarded.

Question 14Workshop safety, tools and equipment

A technician is drilling a 12 mm hole in a steel plate on a pillar drill. The plate is held by hand because the drill vice is in use. Why is this practice unsafe?

  1. The drill will run at the wrong speed without a vice
  2. The rotating drill can snatch the plate and spin it, causing injury Correct answer.
  3. The hole will be drilled off-centre and the plate will be scrapped
  4. The drill bit will overheat because hand pressure is uneven

Explanation

A pillar drill can grab a hand-held workpiece when the bit breaks through or catches, spinning the plate with high torque. The correct practice is to clamp the workpiece in a drill vice or hold it with clamps bolted to the table. Hand holding is never acceptable for metal drilling on a powered drill.

Question 15Workshop safety, tools and equipment

A portable electric hand lamp is needed to inspect inside a wet wheel arch of a car. The lamp has a metallic guard and a 230 V filament bulb. What is the correct safety measure?

  1. Wrap the lamp handle in insulating tape and proceed
  2. Plug the lamp into any available socket because the metal guard is earthed
  3. Stand on a dry wooden board and hold the lamp with rubber gloves
  4. Use a battery-operated or 24 V extra-low-voltage lamp instead Correct answer.

Explanation

In a wet or damp location, a 230 V hand lamp with a filament bulb is a shock risk if the cable or fitting is damaged. Battery-operated or 24 V extra-low-voltage lamps are the correct choice because the supply is isolated from earth and the shock potential is much lower. Earthing alone does not make a portable lamp suitable for wet areas.

Question 16Workshop safety, tools and equipment

A technician must lower a manual gearbox from a front-wheel-drive car in the workshop. Which equipment is the correct choice for supporting and lowering the gearbox safely?

  1. Two axle stands placed under the bell housing
  2. A transmission jack with an adjustable cradle and safety chain Correct answer.
  3. A length of rope passed through the gearbox mounting holes
  4. A hydraulic trolley jack placed under the gearbox casing

Explanation

A transmission jack has a wide, adjustable cradle and a safety chain or strap to hold the gearbox securely while it is lowered. A trolley jack has a small saddle that lets a heavy, awkward gearbox slip, and it is not designed for off-centre loads. Axle stands and rope do not provide controlled lowering.

Question 17Engine construction, operation and overhaul

In a four-stroke petrol engine, which stroke immediately follows the compression stroke?

  1. Power stroke Correct answer.
  2. Intake stroke
  3. Valve overlap stroke
  4. Exhaust stroke

Explanation

The four-stroke cycle always runs intake, compression, power and exhaust in that fixed order for each cylinder. The charge is ignited near the end of compression, so the expanding gases push the piston down on the power stroke.

Question 18Engine construction, operation and overhaul

Which component is bolted to the top face of the cylinder block to close the combustion chambers of an overhead-valve engine?

  1. Oil sump pan
  2. Cylinder head Correct answer.
  3. Flywheel housing
  4. Inlet manifold

Explanation

The cylinder head sits on the top face of the block and forms the roof of each combustion chamber, carrying the valves and spark plugs or injectors. With the head gasket it seals every bore so that compression and combustion pressure are contained.

Question 19Engine construction, operation and overhaul

Which piston ring is fitted in the lowest groove of the piston and mainly controls the oil film on the cylinder wall?

  1. Second compression ring
  2. Snap ring
  3. Oil control ring Correct answer.
  4. Top compression ring

Explanation

The lowest groove normally carries the oil control ring, whose rails scrape surplus oil from the bore and return it through drain holes to the sump. The upper grooves hold the compression rings, which seal combustion gases against the piston crown.

Question 20Engine construction, operation and overhaul

The specified cold valve clearance is 0.20 mm, but a technician measures 0.45 mm at one intake valve on an overhead-cam engine with rocker adjustment. What is the most likely result?

  1. The valve will overheat because it cannot seat
  2. Late opening, reduced lift and tappet noise Correct answer.
  3. The valve will open earlier and lift further
  4. Oil consumption will rise from a damaged stem seal

Explanation

Clearance is the gap between the cam or rocker and the valve stem tip, so an oversized gap means the cam must turn further before it touches the stem. Opening is therefore delayed, lift and duration are reduced, and the extra gap produces a sharp ticking noise as the rocker strikes the stem.

Question 21Engine construction, operation and overhaul

Why are cylinder head bolts on an aluminium engine tightened with a torque wrench in a specified sequence and in stages?

  1. To reduce the time needed for the job
  2. To compress the valve springs fully before starting
  3. To stretch the head bolts beyond their elastic limit deliberately
  4. To spread clamping load evenly and avoid gasket leaks Correct answer.

Explanation

Staged, sequenced tightening (usually spiral or diagonal from the centre outwards) spreads the clamp force evenly across the joint. This prevents a light alloy head from warping, keeps the gasket evenly compressed and avoids leaks or fretting at the block face.

Question 22Engine construction, operation and overhaul

During an overhaul, a new top compression ring shows an end gap of 0.25 mm in the bore against a specification of 0.30 to 0.45 mm. What is the correct action?

  1. Hone the bore until the gap opens to the specification
  2. Fit the ring as it is, because a small gap is always safe
  3. Grind the ring ends squarely until the gap is in specification Correct answer.
  4. Fit a second ring on top of the first to take up the clearance

Explanation

End gap is checked by squaring the ring in the bore with a piston and measuring the gap with a feeler gauge. If the gap is below specification the ring ends are filed or ground squarely until the gap falls within range, because a tight gap butts closed when the ring expands with heat.

Question 23Engine construction, operation and overhaul

A timing belt on an interference engine jumps two teeth while the engine is running. What is the most likely consequence?

  1. Only the ignition timing shifts, so power drops slightly
  2. The oil pump stops and the bearings seize
  3. Nothing, because the tensioner resets the timing automatically
  4. Valves may contact the pistons and be bent Correct answer.

Explanation

In an interference engine the piston crown and a fully open valve occupy the same space at different moments, so valve timing must stay exact. When a belt or chain jumps teeth, the pistons can strike valves that are open at the wrong time, bending stems and damaging pistons and the head.

Question 24Engine construction, operation and overhaul

A technician checks connecting rod bearing clearance with Plastigauge. Which procedure gives a valid reading?

  1. Torque the cap over the strip on the dry journal and read the flattened width Correct answer.
  2. Lay the strip on the outside of the bearing cap and read it hot
  3. Run the engine for ten minutes after torquing, then read the strip
  4. Insert a feeler gauge between the bearing shell and the crankshaft journal while the engine idles at speed

Explanation

Plastigauge is a crushable plastic thread of known thickness. A piece is laid along the clean, dry journal, the cap is fitted and torqued to specification without turning the shaft, and the flattened width is matched to the printed scale to give the clearance.

Question 25Engine construction, operation and overhaul

A cylinder bore measures 80.00 mm at the top of ring travel and 79.94 mm at the bottom, and the service limit for taper is 0.05 mm. What does this indicate?

  1. Taper is beyond the limit, so rebore or resleeve Correct answer.
  2. Out-of-round bore that needs only light honing
  3. Normal wear, so only new piston rings are required
  4. A faulty micrometer, because bores wear most at the bottom

Explanation

Taper is the difference between diameters measured at the top of ring travel and near the bottom, in both thrust directions. A taper of 0.06 mm exceeds the 0.05 mm limit, so honing cannot correct it and the cylinder must be rebored to the next oversize or resleeved.

Question 26Engine construction, operation and overhaul

A four-cylinder diesel gives 18 bar dry compression on one cylinder while the others give about 30 bar. After a spoonful of oil is added, that cylinder reads 29 bar. What is the most probable cause?

  1. Incorrect fuel injection timing
  2. Leaking intake valve seats
  3. A blown head gasket between two cylinders
  4. Worn piston rings and cylinder bores Correct answer.

Explanation

Adding oil temporarily seals the gap between rings and bore, so a wet reading that climbs close to the other cylinders shows the leakage was past the rings. Valve or gasket leakage would not be sealed by oil and the wet reading would stay low.

Question 27Engine construction, operation and overhaul

On a four-wheeler engine, what is the main function of the flywheel?

  1. To raise compression pressure inside the cylinder at high speed
  2. To open and close the valves in step with the pistons
  3. To multiply engine torque before it reaches the gearbox
  4. To smooth out torque pulses and store energy Correct answer.

Explanation

The flywheel has enough mass to absorb energy during the power stroke and release it during the other strokes, so crankshaft speed stays fairly steady. It also carries the starter ring gear and provides a friction surface for the clutch. Torque multiplication is done by the gearbox and final drive, not by the flywheel.

Question 28Engine construction, operation and overhaul

Which component connects the small end of the connecting rod to the piston and allows the rod to pivot as the piston moves?

  1. The crankshaft main journal
  2. The camshaft follower
  3. The crankpin
  4. The gudgeon pin Correct answer.

Explanation

The gudgeon pin, also called the piston pin, passes through the piston pin bosses and the small-end bush of the connecting rod. It lets the rod swing while the piston travels straight in the bore. The crankpin is the big-end journal on the crankshaft.

Question 29Engine construction, operation and overhaul

The profile of a camshaft lobe determines which valve characteristic?

  1. The fitted length of the valve spring
  2. The diameter of the valve stem
  3. The included angle of the valve seat
  4. Valve lift and opening duration Correct answer.

Explanation

The height of the cam lobe sets the maximum valve lift, while the shape of the flanks and the lobe width set when the valve opens, how long it stays open, and when it closes. Valve seat angle is machined into the cylinder head, and stem diameter is a fixed valve dimension.

Question 30Engine construction, operation and overhaul

Why does a precision engine bearing shell have a locating tab at one end?

  1. To set the oil clearance between shell and journal
  2. To allow the bearing to be reused after polishing the journal
  3. To centre the connecting rod on the crankshaft journal
  4. To stop the shell rotating and sliding in its housing Correct answer.

Explanation

The tab fits into a matching groove in the cap or block and prevents the shell from spinning or walking endwise under load. Oil clearance is set by the shell thickness and journal diameter, not by the tab. Precision bearings are replaced, not reused, once worn or damaged.

Question 31Engine construction, operation and overhaul

When checking piston-to-bore clearance during an overhaul, where is the piston measured with a micrometer?

  1. At the bottom of the skirt in line with the pin bore
  2. Across the skirt, 90° to the pin, at the stated height Correct answer.
  3. Across the ring lands at the top of the piston
  4. Across the crown in line with the piston pin

Explanation

Pistons are made slightly oval and tapered, and the specified measuring point is on the skirt at right angles to the gudgeon pin, at a stated height below the pin centre. The bore is measured at the same height so the clearance is comparable. Measuring across the pin line or at the crown gives a false, smaller reading.

Question 32Engine construction, operation and overhaul

A valve guide clearance is measured at 0.20 mm against a service limit of 0.10 mm. What is the correct repair?

  1. Increase valve spring tension to take up play
  2. Fit a larger valve stem oil seal
  3. Grind the valve stem to reduce its diameter
  4. Renew the guide and ream to size Correct answer.

Explanation

Excessive guide clearance lets the valve wobble, which causes poor seat contact, oil consumption and rapid seat wear. The worn guide is replaced and reamed or honed to give the specified clearance with the valve stem. Grinding the stem or fitting a bigger seal does not restore correct guidance.

Question 33Engine construction, operation and overhaul

A dial gauge shows 0.35 mm of crankshaft end play against a limit of 0.25 mm. Which component normally controls this end play?

  1. Main bearing oil seals
  2. The connecting rod big-end bearings
  3. The flywheel ring gear
  4. The thrust main bearing shell Correct answer.

Explanation

One main bearing is usually a thrust bearing with flanged faces that limit axial movement of the crankshaft. End play is measured with a dial gauge while the crankshaft is levered fore and aft. Excessive play means the thrust faces or crankshaft thrust surface are worn.

Question 34Engine construction, operation and overhaul

A cast-iron cylinder head is checked for flatness with a straight edge and feeler gauge. The maximum warp across the centre is 0.12 mm and the manufacturer's limit is 0.05 mm. What is the correct action?

  1. Reuse it because cast iron heads do not warp at all
  2. Resurface within the stated limit, or replace the head Correct answer.
  3. Reuse it with a thicker head gasket and retorque it
  4. Grind until flat and fit a standard gasket

Explanation

Warpage beyond the limit prevents the head gasket from sealing and can distort camshaft bore alignment. The head may be resurfaced only within the manufacturer's maximum material removal limit; if that much cutting would be needed, the head is replaced. A thicker gasket does not correct a warped face.

Question 35Engine construction, operation and overhaul

New wet cylinder liners are fitted to a diesel engine block. Liner protrusion above the deck measures 0.03 mm, while the specification is 0.08–0.12 mm. What is the most likely consequence if the engine is assembled as it is?

  1. Increased crankshaft end play when hot
  2. Poor piston ring bedding during running-in
  3. Retarded injection timing of several degrees
  4. Head gasket leakage and compression loss Correct answer.

Explanation

The liner protrusion provides the clamping load that compresses the head gasket fire ring around each cylinder. If protrusion is too small, combustion gas or coolant can escape past the gasket, causing compression loss, overheating or coolant entering the cylinder. The liner seat and shims must be corrected before assembly.

Question 36Engine construction, operation and overhaul

A four-cylinder four-stroke engine has a bore of 80 mm and a stroke of 90 mm. Using swept volume = (π/4) × bore² × stroke × number of cylinders, what is the approximate engine displacement?

  1. About 1440 cc
  2. About 1810 cc Correct answer.
  3. About 905 cc
  4. About 2260 cc

Explanation

One cylinder displaces (π/4) × 80² × 90 = 452,389 mm³, which is about 452 cc. Multiplying by four cylinders gives about 1,810 cc, or 1.81 litres. The other figures result from using the wrong number of cylinders or an incorrect formula.

Question 37Engine construction, operation and overhaul

In a four-wheeler engine cooling system, what is the primary job of the thermostat?

  1. It raises the boiling point of the coolant by pressurising the radiator.
  2. It filters rust and scale out of the coolant before it reaches the radiator.
  3. It drives the coolant through the radiator and engine passages.
  4. It regulates coolant flow to hold the engine at normal operating temperature. Correct answer.

Explanation

The thermostat is a temperature-controlled valve in the coolant path. It stays closed while the engine is cold to speed warm-up, then opens progressively to send coolant through the radiator and limit overheating.

Question 38Engine construction, operation and overhaul

A camshaft is checked with a degree wheel. The intake valve opens at 10° before top dead centre and closes at 40° after bottom dead centre. What is the intake valve duration?

  1. 40°
  2. 190°
  3. 230° Correct answer.
  4. 220°

Explanation

Duration is the total crank angle the valve is off its seat. From 10° before TDC to TDC is 10°, TDC to BDC is 180°, and BDC to 40° after BDC is 40°, giving 10 + 180 + 40 = 230°.

Question 39Engine construction, operation and overhaul

A four-cylinder in-line four-stroke engine fires in the order 1-3-4-2. When cylinder 1 is at top dead centre on the compression stroke, which cylinder is at top dead centre with its valves in overlap?

  1. Cylinder 2
  2. Cylinder 3
  3. No other cylinder, because only one piston can be at TDC at a time.
  4. Cylinder 4 Correct answer.

Explanation

In an in-line four, pistons 1 and 4 reach TDC together and pistons 2 and 3 reach BDC together. With firing order 1-3-4-2, when No. 1 is on compression TDC, No. 4 is 360° crank degrees away on exhaust TDC, where intake and exhaust valves overlap.

Question 40Engine construction, operation and overhaul

A four-stroke diesel engine has a compression ratio of 18:1. The swept volume of one cylinder is 600 cm³. What is the clearance volume of that cylinder?

  1. 35.3 cm³ Correct answer.
  2. 600 cm³
  3. 31.6 cm³
  4. 33.3 cm³

Explanation

Compression ratio CR = (swept volume + clearance volume) / clearance volume, so clearance volume = swept volume / (CR − 1). Here 600 / (18 − 1) = 600 / 17 ≈ 35.3 cm³.

Question 41Fuel supply, injection and emission control systems

On a port fuel injection petrol engine, what is the main job of the electric fuel pump mounted in the fuel tank?

  1. To circulate coolant through the throttle body during cold start
  2. To create the high-voltage spark required by the ignition coil
  3. To deliver fuel from the tank to the injectors at the pressure required by the injection system Correct answer.
  4. To remove water and dirt from the fuel before it reaches the rail

Explanation

The tank-mounted electric pump supplies liquid fuel under pressure to the injection system. The ECU and fuel pressure regulator then manage the pressure at the injectors. Cleaning the fuel is the filter's task, and spark generation belongs to the ignition system.

Question 42Fuel supply, injection and emission control systems

What is the purpose of the fuel filter in a four-wheeler fuel supply system?

  1. To cool the fuel returning to the tank so that vapour lock is prevented during hot weather
  2. To increase the octane rating of the petrol so that knocking is reduced under load
  3. To mix air with fuel before the throttle plate
  4. To trap dirt and rust particles that could block or damage injectors and the pump Correct answer.

Explanation

The fuel filter is a barrier that captures dirt, rust and other solid contaminants before they reach precision components. Clean fuel is essential because injectors have very small passages that are easily blocked. The filter does not change octane rating, cool the fuel or mix air with fuel.

Question 43Fuel supply, injection and emission control systems

In the exhaust system of a petrol car, what is the primary function of the three-way catalytic converter?

  1. To reduce the noise level of the exhaust gases before they leave the tailpipe
  2. To store fuel vapour from the tank until the engine can burn it
  3. To increase exhaust back pressure so that the turbocharger spools faster
  4. To convert hydrocarbons, carbon monoxide and nitrogen oxides into less harmful gases Correct answer.

Explanation

A three-way catalytic converter promotes chemical reactions that oxidise hydrocarbons and carbon monoxide and reduce nitrogen oxides. It therefore lowers the harmful content of the exhaust gas. Noise reduction is done by the silencer, and fuel vapour storage is done by the EVAP canister.

Question 44Fuel supply, injection and emission control systems

How does a vacuum-referenced fuel pressure regulator on a port fuel injection engine respond when intake manifold vacuum increases at idle?

  1. It lowers rail pressure because manifold vacuum assists the fuel pressure in opening the return valve Correct answer.
  2. It holds the rail pressure constant regardless of changes in manifold vacuum
  3. It closes the return line completely to raise pressure during cold starting
  4. It increases the pressure in the fuel rail in direct proportion to the rise in manifold vacuum

Explanation

The regulator uses manifold vacuum on the diaphragm to keep the pressure difference across the injector nearly constant. When vacuum rises, less fuel pressure is needed to open the return valve, so rail pressure falls. This compensation keeps the injected fuel quantity correct as manifold pressure changes.

Question 45Fuel supply, injection and emission control systems

What does the mass air flow (MAF) sensor tell the engine control unit in a modern petrol engine?

  1. The position of the accelerator pedal, so the ECU can control the throttle motor
  2. The mass of air entering the engine, so the ECU can calculate the required fuel mass Correct answer.
  3. The pressure of fuel in the rail, so the ECU can set the injection timing
  4. The amount of oxygen stored in the catalytic converter after combustion

Explanation

The MAF sensor measures the actual mass of air drawn into the engine. The ECU uses that value, together with the target air-fuel ratio, to calculate the base fuel quantity. Fuel rail pressure, oxygen storage and accelerator pedal position are measured by other sensors.

Question 46Fuel supply, injection and emission control systems

When a petrol engine is running in closed-loop fuel control, how does the ECU use the upstream oxygen sensor signal?

  1. It adjusts injector pulse width to keep the exhaust mixture close to stoichiometric Correct answer.
  2. It ignores the signal and fuels only from a fixed map stored in memory
  3. It uses the signal to set the ignition timing to the knock limit
  4. It opens the EVAP purge valve only when the sensor voltage is high

Explanation

In closed loop the ECU compares the oxygen sensor signal with the stoichiometric target. It then makes small corrections to injector pulse width so that the mixture stays near that target. This feedback allows the system to compensate for wear, deposits and small air leaks.

Question 47Fuel supply, injection and emission control systems

What is the main purpose of exhaust gas recirculation (EGR) on a petrol or diesel engine?

  1. To burn unburned fuel that has escaped from the cylinder during valve overlap
  2. To lower combustion peak temperature and reduce nitrogen oxide formation Correct answer.
  3. To supply extra air for combustion when the turbocharger is not producing boost
  4. To increase the oxygen content of the intake charge for better power

Explanation

EGR sends a controlled portion of exhaust gas back into the intake. This inert gas dilutes the fresh charge and lowers peak combustion temperature. Lower peak temperature suppresses the formation of nitrogen oxides.

Question 48Fuel supply, injection and emission control systems

In an electronic fuel injection system, what mainly determines the injector pulse width during normal running?

  1. The opening pressure of the fuel pump relief valve and the tank level
  2. The electrical resistance of the injector coil and the total length of its wiring harness in the vehicle
  3. The size of the throttle plate and the volume of the intake manifold
  4. The ECU's calculation of the air mass entering the engine and the target air-fuel ratio Correct answer.

Explanation

The ECU calculates the base fuel mass from measured air mass and the target air-fuel ratio. It converts that fuel mass into an injector opening time, then trims it using feedback and corrections. Injector resistance and wiring length affect current flow, but they do not set the normal pulse width.

Question 49Fuel supply, injection and emission control systems

A petrol car shows a long-term fuel trim of +28% on bank 1 with a normal MAF reading and no injector fault codes. Which condition is the most likely cause?

  1. A fuel pressure regulator that is stuck closed and raising rail pressure
  2. An unmetered air leak into the intake manifold after the MAF sensor Correct answer.
  3. A leaking exhaust valve that is sending extra air into the cylinder
  4. A fuel injector that is stuck open and delivering too much fuel

Explanation

A positive long-term fuel trim means the ECU is adding fuel because the mixture has been lean. Air entering after the MAF sensor is not measured, so the ECU fuels for less air than the engine actually receives. A normal MAF reading makes an air leak downstream of the sensor the most likely cause among the choices.

Question 50Fuel supply, injection and emission control systems

On a common rail diesel engine, what is the role of the rail pressure sensor?

  1. It measures the amount of air entering the intake manifold for smoke limiting
  2. It reports actual fuel pressure in the rail so the ECU can regulate the pressure control valve Correct answer.
  3. It senses the position of the camshaft so that injection timing can be synchronized
  4. It controls the opening time of each injector solenoid directly without any signal from the engine control unit

Explanation

The rail pressure sensor provides the ECU with a feedback signal of actual fuel pressure in the common rail. The ECU compares this with the desired pressure and commands the pressure control valve accordingly. Injector opening, air measurement and camshaft position are handled by other sensors and actuators.