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Exam Review

Key Facts: Motor Mechanic Trade Test Exam

100

Practice Questions

OpenExamPrep

2-3 days

Trade Test Duration

QCTO

60%

Typical Pass Mark

QCTO

QCTO/NAMB

Administered By

QCTO

Petrol

Spark-Ignition Trade

OpenExamPrep

14.7:1

Stoichiometric Air-Fuel Ratio

Trade theory

The Motor Mechanic artisan trade test is South Africa's national assessment for qualifying as a petrol motor mechanic, administered through the QCTO and NAMB framework. It is a competence-based trade test of written and practical tasks conducted over two to three days at a QCTO-accredited trade test centre by a NAMB-registered assessor, and access is commonly gained through an N2 certificate with relevant trade-theory subjects plus workplace experience or an RPL route. The trade theory covers petrol engine theory, fuel/ignition and EFI systems, transmission and driveline, brakes/steering/suspension, electrical and electronics, diagnostics, and safety, using South African terminology. This free prep includes 100 research-based practice questions with explanations and an AI tutor.

Sample Motor Mechanic Trade Test Practice Questions

Try these sample questions to review concepts for the Motor Mechanic Trade Test exam. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1In a four-stroke petrol engine, in what order do the four strokes occur during one complete cycle?
A.Compression, induction, power, exhaust
B.Induction, compression, power, exhaust
C.Power, exhaust, induction, compression
D.Induction, power, compression, exhaust
Explanation: A four-stroke petrol (Otto-cycle) engine completes induction (intake), compression, power (combustion/expansion), and exhaust in that sequence over two crankshaft revolutions. Fuel-air mixture is drawn in, compressed, ignited to produce power, then burnt gases are expelled.
2How many crankshaft revolutions are required to complete one full cycle of a four-stroke petrol engine?
A.One revolution
B.Two revolutions
C.Three revolutions
D.Four revolutions
Explanation: A four-stroke engine needs two complete crankshaft revolutions (720 degrees) to complete one cycle, because each stroke corresponds to half a crankshaft turn and there are four strokes. This is why the camshaft turns at half crankshaft speed.
3The camshaft of a four-stroke engine rotates at what speed relative to the crankshaft?
A.The same speed as the crankshaft
B.Twice crankshaft speed
C.Half crankshaft speed
D.Quarter crankshaft speed
Explanation: Because each valve opens once every two crankshaft revolutions, the camshaft must rotate at half engine (crankshaft) speed. The timing gears or belt are therefore geared 2:1, with the camshaft sprocket having twice as many teeth as the crankshaft sprocket.
4Compression ratio of a petrol engine is best defined as the ratio of the cylinder volume when the piston is at:
A.BDC to the volume at TDC
B.TDC to the volume at BDC
C.Mid-stroke to the volume at TDC
D.BDC to the swept volume only
Explanation: Compression ratio = total cylinder volume with the piston at bottom dead centre (swept + clearance volume) divided by the clearance volume with the piston at top dead centre. Typical petrol engines run around 9:1 to 11:1, lower than diesels to avoid detonation.
5On which stroke does the spark plug ignite the air-fuel mixture in a petrol engine?
A.Near the end of the induction stroke
B.Near the end of the compression stroke
C.At the start of the exhaust stroke
D.In the middle of the power stroke
Explanation: The spark occurs just before the piston reaches TDC at the end of the compression stroke (ignition advance), so peak combustion pressure develops shortly after TDC to drive the power stroke. Igniting the fully compressed charge maximises efficiency and power.
6The most common firing order for a four-cylinder in-line petrol engine is:
A.1-2-3-4
B.1-3-4-2
C.1-4-2-3
D.1-2-4-3
Explanation: The firing order 1-3-4-2 is the most widely used for in-line four-cylinder engines because it spreads the power impulses evenly and balances the loading on the crankshaft, reducing vibration. 1-2-4-3 is also used on some engines but 1-3-4-2 is the classic.
7The clearance between the rocker/cam and the valve stem when the valve is fully closed is called the:
A.Valve overlap
B.Valve clearance (tappet clearance)
C.Valve lift
D.Valve lead
Explanation: Valve (tappet) clearance is the small gap left in the valve train when the valve is closed to allow for thermal expansion of the components as the engine heats up. Too little clearance can hold valves open and burn them; too much causes noisy operation and reduced lift.
8Valve overlap is the period during which:
A.Both the inlet and exhaust valves are open at the same time near TDC
B.Both valves are closed during compression
C.The inlet valve opens before the exhaust closes near BDC
D.The exhaust valve stays open during the whole power stroke
Explanation: Valve overlap occurs near the end of the exhaust and start of the induction stroke (around TDC) when both the inlet and exhaust valves are open simultaneously. It uses the momentum of the exhaust gas to help draw in fresh charge, improving cylinder filling (scavenging).
9Pre-ignition in a petrol engine is best described as:
A.Ignition of the charge by a hot spot before the spark occurs
B.The spark occurring exactly at TDC
C.Detonation after the spark caused by low octane fuel
D.Failure of the spark plug to fire at all
Explanation: Pre-ignition is uncontrolled combustion that starts before the spark, caused by a hot spot such as glowing carbon, an overheated spark plug, or sharp edges in the chamber. It raises pressures and temperatures abnormally and can quickly damage pistons.
10Detonation (knocking) in a petrol engine is most likely to be reduced by:
A.Using a lower octane fuel
B.Increasing the compression ratio
C.Using a higher octane fuel
D.Advancing the ignition timing further
Explanation: Detonation is the spontaneous explosion of the remaining end-gas after the spark, producing a metallic knock. A higher octane fuel resists auto-ignition, so it reduces or eliminates knock. Retarding timing and lowering compression also help.

About the Motor Mechanic Trade Test Exam

The South African Motor Mechanic artisan trade test is the national assessment that qualifies a petrol motor mechanic as a recognised artisan. It is a competence-based test of written and practical tasks conducted over two to three days at a QCTO-accredited trade test centre by an assessor registered with the National Artisan Moderation Body (NAMB), and is distinct from the diesel mechanic trade.

Exam sponsor: Quality Council for Trades and Occupations (QCTO) / National Artisan Moderation Body (NAMB). The requirements and fees below concern the certification or admission exam, separate from our free practice resources.

Assessment

Competence-based trade test of written (knowledge) and practical tasks over 2-3 days at a QCTO-accredited centre, assessed by a NAMB-registered assessor; this practice bank is 100 selected-response trade-theory items

Time Limit

Conducted over a minimum of 2 and a maximum of 3 days

Passing Score

60% (standard QCTO trade-test pass mark; confirm with your centre)

Exam / Certification Fees

Trade-test fee varies by accredited centre; confirm the current amount when booking

Exam sponsor website

Fees, eligibility, and exam policies can change. Confirm them with the exam sponsor before applying or paying.

Our practice resources: topics covered

We aim to reflect publicly available exam outlines and topic information in our study resources. Coverage, format, and difficulty may differ from the actual exam, and we cannot guarantee that every detail is accurate or current. Confirm exam requirements, fees, and policies with the official exam sponsor.

18%

Petrol Engine Theory

Four-stroke cycle, firing orders, compression ratio, valve timing and overlap, valve clearance, combustion faults, octane, cooling and lubrication, pistons, rings and flywheel

22%

Fuel, Ignition & EFI

Carburettor and EFI, the ECU and sensors (MAP, TPS, crank, coolant, oxygen, knock), injectors, fuel pump and regulator, ignition coils, distributorless systems, air-fuel ratio and emissions

16%

Transmission & Driveline

Clutch, manual gearbox and synchromesh, gear ratios, propeller shaft and universal/CV joints, differential and final drive, and automatic torque converters

18%

Brakes, Steering & Suspension

Hydraulic disc and drum brakes, master cylinder and servo, ABS, brake fluid and bleeding, rack-and-pinion steering, alignment geometry, springs, dampers and anti-roll bars

12%

Electrical & Electronics

Lead-acid battery, Ohm's law, charging and starting systems, relays, fuses, multimeter measurement and electrical fault-finding

8%

Diagnostics

Logical fault-finding, exhaust smoke and compression diagnosis, OBD-II scan tools, misfire and head-gasket faults, and mixture problems

6%

Safety

Safe jacking, carbon monoxide and battery hazards, fire extinguishers, PPE, and the QCTO/NAMB trade-test framework

Preparing for the Motor Mechanic Trade Test Exam

What You Need to Know

  • Passing score: 60% (standard QCTO trade-test pass mark; confirm with your centre)
  • Assessment: Competence-based trade test of written (knowledge) and practical tasks over 2-3 days at a QCTO-accredited centre, assessed by a NAMB-registered assessor; this practice bank is 100 selected-response trade-theory items
  • Time limit: Conducted over a minimum of 2 and a maximum of 3 days
  • Exam / certification fees: Trade-test fee varies by accredited centre; confirm the current amount when booking Official sources

Using Our Practice Resources

  • Work through all 100 available questions
  • Review every answer and explanation
  • Track weak areas and revisit them
  • Use our AI tutor for tough concepts

Motor Mechanic Trade Test: Suggested Study Strategy

1Master the four-stroke cycle, firing order 1-3-4-2 for an in-line four, compression ratio and valve overlap before moving to systems
2Know your EFI sensors cold: what the MAP, TPS, crankshaft, coolant, oxygen (lambda) and knock sensors each tell the ECU
3Remember the stoichiometric petrol air-fuel ratio is about 14.7:1 and why closed-loop control keeps the catalytic converter working
4Practise diagnosing by exhaust smoke colour: blue is oil, black is rich mixture, white is coolant/head gasket
5Use South African terminology and standards (N2 trade theory, QCTO/NAMB framework) rather than overseas codes
6Complete all 100 practice questions and review every miss with the AI tutor before your trade test

Frequently Asked Questions

How is the South African motor mechanic trade test conducted?

It is a competence-based artisan trade test of written and practical tasks conducted over two to three days at a QCTO-accredited trade test centre by an assessor registered with the National Artisan Moderation Body (NAMB). The exact number of theory questions is not publicly published.

What pass mark do I need for the motor mechanic trade test?

QCTO artisan trade tests generally require 60% to be found competent, and you must pass both the knowledge and practical components. Always confirm the current requirement with your accredited trade test centre when you book.

What are the entry requirements for the motor mechanic trade test?

The common route is an N2 certificate with relevant trade-theory subjects plus relevant workplace experience through an apprenticeship or learnership. Experienced workers may also access the trade test through a Recognition of Prior Learning (RPL) route.

Is the motor mechanic trade test the same as the diesel mechanic trade test?

No. The motor mechanic trade focuses on petrol (spark-ignition) engines and their fuel, ignition and EFI systems, while the diesel mechanic trade focuses on compression-ignition engines and diesel fuel injection. They are separate designated trades.

What topics does the motor mechanic trade theory cover?

It covers petrol engine theory, fuel/ignition and EFI systems, transmission and driveline, brakes/steering/suspension, electrical and electronics, diagnostics, and workshop safety, all using South African terminology and standards.

Is this free motor mechanic trade test practice useful for preparation?

Yes. Our 100 research-based questions cover the full trade-theory syllabus with a teaching explanation for every answer, plus free daily AI tutor interactions. All content is free forever and updated for 2026 to help you prepare for the knowledge component.