Five free practice questions on engines, fuel and aftertreatment systems: block B of the Red Seal 310T Truck and Coach Technician exam, about 21 of its 135 questions. They are in the exam's format: four options, one correct answer. Answer each one before opening the explanation. No account, no email.
01The questions
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A tractor shuts down intermittently on rough roads and restarts immediately. The ECM logs a code for loss of the crankshaft position signal at each event, and the sensor tests within specification on the bench. What is the most likely cause?
- A failing crankshaft position sensor.
- Low fuel pressure on rough roads.
- A connection opening under vibration.
- A faulty ECM.
Show the answer
C. Correct. An intermittent shutdown tied to rough road, with a signal-loss code and a sensor that bench-tests fine, is the signature of a connector or harness fault that opens momentarily when jolted: a spread terminal, corrosion in the connector, or a chafed wire. The RSOS lists engine shutdowns among symptoms and poor connections and chafed or corroded harnesses among failures; the technician wiggle-tests the sensor connector and harness while watching live data, and checks terminal tension.
Why not the others
A. The sensor tests good, and a sensor failing internally does not usually correlate with road roughness. The pattern points to something the bumps disturb.
B. Fuel starvation causes a stumble or stall with a fuel-related code, and the engine would not restart instantly. The crank signal code identifies the circuit.
D. An ECM fault would not be selective to rough roads or to one sensor circuit. The evidence sits in the wiring between sensor and module.
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A tractor's oil pressure warning comes on at idle only after the engine is fully warm; at highway speed pressure is normal, and the oil level and grade are correct. What is the most likely cause?
- Worn crankshaft bearings.
- A faulty oil pressure sender.
- A stuck-open pressure regulator valve.
- A plugged oil filter.
Show the answer
A. Correct. Bearing clearance grows with wear, and hot, thin oil escapes through it faster than the pump can supply at idle speed; at higher rpm the pump keeps up and pressure recovers. Low pressure that appears only hot and only at idle is the classic bearing-wear pattern. The RSOS lists low oil pressure among symptoms; the technician confirms with a mechanical gauge, checks the oil sample for bearing metals, and inspects bearings per the manufacturer's procedure.
Why not the others
B. A sender can fail, and it is checked first with a mechanical gauge. But a sender fault does not follow engine temperature and speed the way this one does; the pattern is mechanical.
C. A regulator stuck open dumps pressure at all speeds and temperatures, not only at hot idle. The pattern of normal pressure at speed rules it out.
D. A plugged filter opens its bypass and the engine runs on unfiltered oil; it does not produce hot-idle-only low pressure. It would show as high differential across the filter.
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A technician has installed a new DPF on a highway tractor. Which step is required before the repair can be verified?
- Pour DEF into the DPF inlet to condition the substrate.
- Drive the vehicle at highway speed for 50 kilometres to seat the filter.
- Reset the soot and ash accumulation values in the ECM per the manufacturer's procedure.
- Disconnect the differential pressure sensor so it does not read the new filter.
Show the answer
C. Correct. The ECM tracks soot load and ash load by model and sensor data; with a new filter installed those values must be reset with the service tool, or the ECM will call regenerations and service on the old filter's history and may derate the engine. The RSOS states that parameters are reprogrammed after repair, and verification then follows using the listed methods: operating the vehicle, a parked regeneration, and monitoring operation.
Why not the others
A. DEF belongs in the DEF tank only. Wetting the DPF substrate with urea solution damages it.
B. A DPF does not seat. Operating the vehicle is part of verification, but only after the ECM has been told the filter is new.
D. The sensor is how the ECM monitors the new filter. Disconnecting it sets a code and disables regeneration control.
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A driver has been using an ether starting-fluid can on a coach that will not start on cold mornings. The technician finds the engine is fitted with an electric intake air pre-heater. Why is this practice dangerous?
- The intake pre-heater can ignite the ether.
- Ether is illegal to use on diesel engines in Canada.
- Ether washes the oil film off the cylinder walls.
- Ether damages the turbocharger bearings.
Show the answer
A. Correct. Ether is extremely volatile, and a glowing intake heater element or grid ignites it in the intake manifold before it reaches the cylinders, which can blow the intake apart and injure anyone nearby. Engines fitted with intake pre-heaters carry warnings against ether for this reason. The RSOS requires the technician to describe starting aids (pre-heaters, ether injection) and their safe use, and to inspect and test the starting aids; the correct action is to repair the pre-heater so it does its job.
Why not the others
B. Ether starting aids are legal and are factory-fitted on some engines as controlled injection systems. The hazard is specific to engines with intake heaters, where the manufacturer prohibits it.
C. Ether can contribute to wear with heavy use, but that is not the immediate hazard on this engine. The specific danger is the combination of ether with the pre-heater.
D. Ether burns in the cylinders and does not reach the turbo bearings. The hazard is ignition in the intake, not turbo damage.
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A tractor will not start after sitting overnight but starts normally once it has been cranked and primed; once running it is fine all day. The fuel filters are new. What is the most likely cause?
- A weak or dragging starter motor.
- A suction-side air leak.
- Low compression.
- Water in the fuel.
Show the answer
B. Correct. Fuel draining back to the tank overnight, with air taking its place, is the classic overnight no-start that priming cures: a loose fitting or cracked line on the suction side, a leaking primer-pump or filter-housing seal, or a failed check valve that no longer holds fuel in the lines. The RSOS lists check valves and lines among fuel components and no start among symptoms; the technician pressure- or vacuum-tests the suction side and inspects for the air entry point.
Why not the others
A. A weak starter would crank slowly every time. The engine cranks normally; it just has no fuel at the injectors until primed.
C. Low compression causes hard starting every time, hot or cold, and it does not clear up after priming. The fact that priming fixes it points to the fuel supply.
D. Water causes rough running, misfires and injector damage, not a clean overnight no-start that priming resolves.
02Answer key
| Question | Answer | Sub-task |
|---|---|---|
| Q1 | C | Diagnoses engine management systems |
| Q2 | A | Diagnoses base engines |
| Q3 | C | Repairs exhaust systems |
| Q4 | A | Diagnoses intake systems |
| Q5 | B | Diagnoses fuel delivery systems |
03What block B covers
This block covers the diesel engine and the systems that support it. It includes base engine testing and overhaul, lubrication and oil analysis, air intake, turbochargers and VGT, charge air coolers, exhaust aftertreatment such as DPF, EGR, SCR and DEF, ECM parameters and sensor diagnosis, common-rail fuel systems and injectors, engine brakes and exhaust brakes, and cooling systems.
The Red Seal Occupational Standard names this block “Services, diagnoses and repairs engines and supporting systems”. It carries 15.6% of the exam, about 21 of the 135 questions, split across eight tasks. The share column is each task's weight within the block, as the standard publishes it.
| Task and its sub-tasks | Share of block |
|---|---|
| Services, diagnoses and repairs base engines Services base engines; Diagnoses base engines; Repairs base engines | 15% |
| Services, diagnoses and repairs lubrication systems Services lubrication systems; Diagnoses lubrication systems; Repairs lubrication systems | 10% |
| Services, diagnoses and repairs intake systems Services intake systems; Diagnoses intake systems; Repairs intake systems | 13% |
| Services, diagnoses and repairs exhaust systems Services exhaust systems; Diagnoses exhaust systems; Repairs exhaust systems | 14% |
| Services, diagnoses and repairs engine management systems Services engine management systems; Diagnoses engine management systems; Repairs engine management systems | 17% |
| Services, diagnoses and repairs fuel delivery systems Services fuel delivery systems; Diagnoses fuel delivery systems; Repairs fuel delivery systems | 13% |
| Services, diagnoses and repairs engine retarder systems Services engine retarder systems; Diagnoses engine retarder systems; Repairs engine retarder systems | 8% |
| Services, diagnoses and repairs cooling systems Services cooling systems; Diagnoses cooling systems; Repairs cooling systems | 10% |
04What the questions turn on
Oil pressure patterns
Low oil pressure only at idle once the engine is hot points to worn crankshaft bearings, because thin oil escapes the clearance faster than the pump supplies it. Uniformly low pressure with clean oil points to a stuck-open regulator or plugged pickup.
Where the coolant is going
Coolant loss with white vapour at the tailpipe, clean oil and a cold pressure test that holds points to an internal EGR cooler leak. A rock-hard upper hose soon after start-up, with the recovery tank overflowing, means combustion gas is entering the coolant.
Aftertreatment causes upstream
DEF is a fixed 32.5 % urea solution, checked with a refractometer. When regenerations become far more frequent, the engine is making extra soot from an injector, EGR or boost fault, so treating only the DPF leaves the cause in place.
Engine brake clues
A compression brake opens the exhaust valves near TDC and is actuated by engine oil, so weak braking on every cylinder with normal commands points to the oil supply. Hammering from one cylinder only while braking means the slave-piston clearance is too wide.
05The other blocks
The 310T exam has 11 blocks. Each has its own page of free questions:
The 310T Truck and Coach Technician practice exam page describes the full question bank. How these questions are written and checked: how our questions are made. Found a mistake? Tell us and we will fix it.