Saudi Skill Verification Program - Light Vehicle Mechanic

What is the primary function of a spark plug in a petrol engine?

• ATo ignite the compressed air-fuel mixture.
• BTo cool the combustion chamber between power strokes.
• CTo lubricate the piston rings inside the cylinder bore.
• DTo measure engine speed for the ignition module.

A compression test shows two adjacent cylinders reading equally low while the other cylinders are normal. What is the most likely cause?

• AA head gasket failed between those two bores.
• BAn overheated catalytic converter downstream.
• CA clogged exhaust manifold restricting flow.
• DA faulty fuel injector on each of those cylinders.

Which component is responsible for filtering contaminants from the fuel before it reaches the injectors in a petrol engine?

• AOil filter
• BCatalytic converter
• CAir filter
• DFuel filter

During an engine timing belt replacement, what critical step must be performed to ensure correct engine operation?

• AReplacing the spark plugs simultaneously.
• BAligning the camshaft and crankshaft timing marks.
• CBleeding air from the brake system.
• DRefilling the engine oil to the correct level.

A petrol engine shows a long-term fuel trim of +22% at idle that falls to about +3% at 2,500 rpm. What is the most likely cause?

• AA restricted exhaust caused by a failing catalytic converter.
• BAn unmetered air leak at the intake manifold gasket.
• CA leaking injector dripping fuel into the intake port.
• DA weak fuel pump that cannot hold rail pressure.

What is the correct technique for lifting a heavy component such as a gearbox from the floor?

• ABend the knees and keep the back straight.
• BBend at the waist and keep the legs straight.
• CTwist while lifting to build up momentum.
• DHold the load at arm's length while lifting.

If an engine's oil pressure warning light illuminates during driving, what immediate action should the driver take?

• AAdd more engine oil while the engine is running.
• BPull over safely and shut off the engine immediately.
• CContinue driving to the nearest service station.
• DAccelerate to clear the warning light.

Which sensor is primarily responsible for measuring the amount of oxygen in the exhaust gases to help the ECU adjust the air-fuel mixture?

• AEngine Coolant Temperature (ECT) sensor
• BManifold Absolute Pressure (MAP) sensor
• CCrankshaft Position (CKP) sensor
• DOxygen sensor (O2 sensor)

After replacing a head gasket, the mechanic must follow specific torque sequences and angles for cylinder head bolts. What is the main reason for this precise procedure?

• ATo maximize fuel efficiency at highway cruising speed.
• BTo clamp the gasket evenly and avoid warping.
• CTo reduce exhaust emissions during engine warm-up.
• DTo prevent spark plug fouling during long idling.

What is the purpose of the engine's cooling system?

• ATo lubricate the crankshaft, camshaft and other moving parts.
• BTo filter contaminants out of the engine oil.
• CTo pressurize the fuel rail for the injectors.
• DTo remove combustion heat and hold operating temperature.

A vehicle has a rough idle and stalls frequently. A vacuum gauge test shows a fluctuating needle. What common issue does this usually indicate?

• ARetarded ignition timing.
• BA restricted exhaust system.
• CA stretched timing chain giving late valve timing.
• DLeaking valves or a worn valve guide.

A petrol engine exhibits a knocking sound that increases with RPM, especially under load. This is not detonation (pre-ignition or pinging). What could be a serious mechanical cause?

• AWorn connecting rod bearings.
• BA faulty alternator bearing.
• CAn overfilled engine oil reservoir.
• DA loose exhaust heat shield.

Which of these is set relative to crankshaft position to control engine performance and fuel economy?

• AIgnition timing
• BThermostat opening temperature
• CAlternator drive belt tension
• DPCV valve flow rate

What type of fuel is used in a petrol engine?

• ADiesel fuel
• BGasoline (Petrol)
• CButane
• DKerosene

Which of the following is NOT a common symptom of a failing fuel pump?

• AEngine cranking but no starting.
• BExcessively high idle speed.
• CLoss of engine power, especially uphill.
• DEngine hesitation or sputtering at high speeds.

A fuel injector is suspected of being faulty. What diagnostic test can be performed to confirm if it's operating correctly?

• AInjector balance test, or a stethoscope click test.
• BMeasuring exhaust gas temperature directly at the manifold.
• CMeasuring ignition coil primary winding resistance.
• DReading manifold absolute pressure sensor voltage at idle.

What is the function of the PCV (Positive Crankcase Ventilation) system in a petrol engine?

• ATo cool the engine oil circulating through the sump.
• BTo lubricate the camshaft lobes and followers.
• CTo supply vacuum to the brake booster.
• DTo vent crankcase blow-by gases into the intake.

A mechanic suspects a clogged catalytic converter. Which diagnostic test would best confirm this suspicion without removing the component?

• AChecking fuel pump delivery pressure at the rail.
• BMeasuring exhaust back pressure before the converter.
• CPerforming a dry compression test on all four cylinders.
• DScanning the ABS module for stored chassis codes.

What is the primary risk of using incorrect spark plugs (e.g., wrong heat range) in a petrol engine?

• ALoss of oil pressure at engine idle.
• BEngine damage from pre-ignition or fouling.
• CContamination of the engine oil with coolant.
• DImmediate failure of the mass airflow sensor.

Which fluid should be checked regularly for proper engine lubrication?

• AEngine oil
• BPower steering fluid
• CBrake fluid
• DWindshield washer fluid

When replacing a timing chain, what other components are commonly replaced as a preventative measure?

• ATiming chain tensioner, guides, and sprockets.
• BFuel tank, fuel lines, and fuel filter.
• CBrake pads, rotors, and calipers.
• DAlternator, starter motor, and battery.

During a cylinder head overhaul, what procedure is essential to ensure proper valve sealing?

• ACutting the valve seats and lapping valves.
• BReplacing the crankshaft position sensor and harness.
• CFlushing and refilling the engine cooling system.
• DRefacing the flywheel and clutch friction surface.

What diagnostic tool is most effective for retrieving diagnostic trouble codes (DTCs) from a vehicle's Engine Control Unit (ECU)?

• ADigital multimeter set to volts and ohms range
• BOscilloscope on a sensor signal wire
• COBD-II scan tool at the diagnostic socket
• DCooling system pressure tester

What is the main purpose of an engine oil filter?

• ATo cool the oil before it reaches the main bearings.
• BTo raise the oil pressure in the galleries.
• CTo hold a reserve of oil for cold starts.
• DTo trap contaminants carried in the engine oil.