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100+ Free SOLAS Heavy Vehicle Mechanic Practice Questions

SOLAS Heavy Vehicles Mechanics Apprenticeship (Ireland) practice questions are available now; exam metadata is being verified.

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2026 Statistics

Key Facts: SOLAS Heavy Vehicle Mechanic Exam

100

Practice Questions

OpenExamPrep

NFQ 6

Award Level (QQI Advanced Certificate Craft)

SOLAS / QQI

4 years

Apprenticeship Duration

SOLAS

7 phases

Programme Structure

SOLAS

No fee

Apprentices Paid Throughout

SOLAS

Ireland

Heavy Vehicle / HGV Craft

SOLAS

The SOLAS Heavy Vehicles Mechanics apprenticeship is Ireland's four-year, NFQ Level 6 craft programme for heavy goods vehicle technicians, administered by SOLAS with QQI certification. It is structured over seven phases (four on-the-job with the employer and three off-the-job in a training centre and colleges) and is assessed by modular multiple-choice and written theory examinations alongside practical and work-based assessments. There is no separate exam fee, and apprentices are paid throughout. Content spans diesel engines and fuel systems, transmission and driveline, full air brake systems, steering and suspension, electrical and electronics, hydraulics, diagnostics and workshop health and safety. This free prep includes 100 research-based practice questions with explanations and an AI tutor.

Sample SOLAS Heavy Vehicle Mechanic Practice Questions

Try these sample questions to test your SOLAS Heavy Vehicle Mechanic exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1In a four-stroke diesel engine, which event occurs during the compression stroke?
A.Air is drawn into the cylinder
B.Air is compressed and fuel is injected near top dead centre
C.Burnt gases are expelled through the exhaust valve
D.The piston is forced down by combustion pressure
Explanation: On the compression stroke the inlet and exhaust valves are closed and the rising piston compresses the trapped air to a high pressure and temperature. Fuel is injected near top dead centre, igniting by compression heat without a spark plug.
2Diesel fuel ignites in the cylinder primarily because of which condition?
A.A high-voltage spark from a glow plug
B.The high temperature of the highly compressed air
C.A carburettor mixing fuel and air before entry
D.Ultraviolet light from the injector
Explanation: Diesel engines are compression-ignition engines. Compressing the air to roughly a 16:1 to 22:1 ratio raises its temperature well above the fuel's auto-ignition point, so injected fuel ignites spontaneously.
3What is the main purpose of a turbocharger on a heavy diesel engine?
A.To cool the engine coolant
B.To force more air into the cylinders to burn more fuel and increase power
C.To reduce the engine's compression ratio
D.To filter particulates from the exhaust
Explanation: A turbocharger uses energy in the exhaust gas to drive a turbine that spins a compressor wheel, forcing a greater mass of air into the cylinders. More air allows more fuel to be burned, raising power and efficiency without increasing engine size.
4Why is an intercooler (charge-air cooler) fitted between the turbocharger and the inlet manifold?
A.To increase the temperature of the boost air
B.To cool the compressed boost air, increasing its density
C.To lubricate the turbocharger bearings
D.To filter the air before the turbo
Explanation: Compressing air in the turbocharger heats it and lowers its density. The intercooler removes heat from the charge air so a denser, oxygen-richer charge enters the cylinders, improving combustion and reducing NOx formation.
5In a modern common-rail diesel injection system, what controls the exact timing and quantity of fuel delivered to each injector?
A.A mechanical inline pump driven by the camshaft
B.The engine ECU energising electronically controlled injectors
C.Engine vacuum acting on a diaphragm
D.The driver's accelerator cable directly opening the injectors
Explanation: Common-rail systems hold fuel at high pressure in a shared rail. The engine ECU commands solenoid or piezo injectors to open for precise durations and timings, allowing multiple injection events per cycle for better combustion, lower emissions and quieter running.
6Approximately what rail pressure can a modern heavy-vehicle common-rail diesel system reach?
A.Around 5 bar
B.Around 50 bar
C.Around 250 bar
D.Up to around 2,000-2,500 bar
Explanation: Modern common-rail systems operate at very high pressures, commonly up to about 2,000-2,500 bar (roughly 29,000-36,000 psi). Such high pressure produces very fine atomisation for cleaner, more complete combustion.
7What is the function of a glow plug in a heavy diesel engine?
A.To provide a spark to ignite the fuel
B.To pre-heat the combustion chamber to aid cold starting
C.To pressurise the fuel rail
D.To meter the air entering the cylinder
Explanation: A glow plug is an electric heating element that warms the combustion chamber (or pre-combustion chamber) before and during cold starts. This raises chamber temperature so the injected fuel ignites reliably when the cold engine cannot otherwise reach auto-ignition temperature.
8Which engine component converts the reciprocating motion of the pistons into rotary motion?
A.The camshaft
B.The crankshaft
C.The flywheel ring gear
D.The rocker arm
Explanation: The crankshaft, driven through the connecting rods, converts the up-and-down (reciprocating) movement of the pistons into rotary motion at the output. Its throws and journals are balanced and supported in main bearings.
9A diesel engine's valve clearance (tappet gap) is too small. What is the most likely consequence?
A.The valves will open later and close earlier
B.The valves may be held slightly open, causing burnt valves and loss of compression
C.Increased valve-train noise but no other effect
D.The injection timing will advance
Explanation: Too little clearance can prevent a valve from seating fully, especially when hot and expanded. A valve held off its seat loses the seat's heat path, overheats and burns, and the cylinder loses compression. Correct clearance must be set to manufacturer specification.
10What does a low reading on an engine oil pressure gauge most commonly indicate?
A.Coolant level is too high
B.Worn bearings, a faulty oil pump, low oil level, or oil that is too thin
C.The air filter is blocked
D.The turbocharger is over-boosting
Explanation: Low oil pressure results from reduced resistance to flow or insufficient supply: worn main/big-end bearings with large clearances, a worn or failing oil pump, low oil level, a stuck-open relief valve, or oil thinned by fuel dilution or overheating. It demands immediate investigation to avoid bearing failure.

About the SOLAS Heavy Vehicle Mechanic Practice Questions

Verified exam format metadata for SOLAS Heavy Vehicles Mechanics Apprenticeship (Ireland) is pending. The practice questions above remain available while official exam length, timing, passing score, fee, and administrator details are reviewed.