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ASE Entry-Level Truck

ASE Entry-Level Diesel Engines — practice test

The Entry-Level Diesel Engines test is one of five ASE Entry-Level Medium/Heavy Truck tests. Students in ASE-accredited diesel programs sit it. ASE builds it from the task list in its Test Specifications and Task Lists, M/H Truck Series, which comes from the 2022 Instructional Standard for program accreditation. It covers the whole engine: head and valve train, block, oil, cooling, air and exhaust, and fuel. Students miss questions by memorizing parts and skipping the why: which gauge, which tool, what a symptom points to, and what to do first. Smoke colors, tool choices and safety steps show up again and again.

Studying for ASE Entry-Level Diesel Engines? Overhaul Prep has 176 verified ETD questions written to the current task list — in the same formats the real exam uses (direct, Technician A/B, EXCEPT and most-likely-cause). Every answer comes with a written explanation, so you learn why instead of memorising a letter.

176ETD questions
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What's on the ASE Entry-Level Diesel Engines test

The test has 40 scored questions, and you need 21 correct to pass. ASE says a test may include extra questions for statistical evaluation that do not count toward your score. The content areas are Fuel System (8 questions), General (7), Cooling System (7), Air Induction, Exhaust Systems, and Engine Brakes (7), Cylinder Head and Valve Train (4), Lubrication System (4), and Engine Block (3). General covers service information, leaks, diagnosis and electronic tools. Fuel, cooling and air together are 22 of the 40 questions, so most of your points come from the systems, not from internal measuring.

ASE Entry-Level task list: Diesel Engines

ASE builds the Entry-Level test on the Test Specifications and Task List in its ASE Test Specifications and Task Lists, M/H Truck Series (2024). In ASE's words: “Every question on the test represents one or more of these tasks, although some tasks may not appear on the version of the test that you see.” This is that list: its 7 content areas, how many questions each one gets, and the 79 tasks the questions are drawn from.

The real test, in ASE's Entry-Level specifications: 40 questions, 21 correct to pass. It may include extra unscored questions.

Test specifications

Content areaQuestions in test
A General7
B Cylinder Head and Valve Train4
C Engine Block3
D Lubrication System4
E Cooling System7
F Air Induction, Exhaust Systems, and Engine Brakes7
G Fuel System8
Total40

The task list, area by area

AGeneral7 questions · 8 tasks
  • 1.Research vehicle service information, including fluid type, vehicle service history, service precautions, and technical service bulletins.
  • 2.Inspect level and condition of fuel, oil, diesel exhaust fluid (DEF), and coolant.
  • 3.Inspect engine assembly for fuel, oil, coolant, air, and other leaks; determine needed action.
  • 4.Diagnose engine operation (starting and running) including: noise, vibration, smoke, etc.; determine needed action.
  • 5.Use appropriate electronic service tool(s) and procedures to diagnose problems; check, record, and clear diagnostic codes; check and record trip/operational data; reset maintenance monitor (if applicable); interpret digital multimeter (DMM) readings.
  • 6.Identify system components, configurations, and types of the following: cylinder head(s), valve train, engine block, engine lubrication, engine cooling, air induction, exhaust, fuel, and engine braking.
  • 7.Diagnose engine no-crank, cranks but fails to start, hard starting, and starts but does not continue to run problems; determine needed action.
  • 8.Diagnose engine surging, rough operation, misfiring, low power, slow deceleration, slow acceleration, and/or shut down problems; determine needed action.
BCylinder Head and Valve Train4 questions · 9 tasks
  • 1.Inspect electronic wiring harness and brackets for wear, bending, cracks, and proper securement; determine needed action.
  • 2.Inspect cylinder head for cracks/damage; check mating surfaces for warpage; check condition of passages; inspect core/expansion and gallery plugs; determine needed action.
  • 3.Inspect injector sleeves and seals; determine needed action.
  • 4.Inspect valve train components; determine needed action.
  • 5.Inspect, measure, and replace/reinstall camshaft; measure end play and backlash; determine needed action.
  • 6.Adjust valve bridges (crossheads); adjust valve clearances and injector settings.
  • 7.Disassemble cylinder head; inspect valves, guides, seats, springs, retainers, rotators, locks, and seals; determine needed action.
  • 8.Measure valve head height relative to deck; measure valve face-to-seat contact; determine needed action.
  • 9.Reassemble cylinder head.
CEngine Block3 questions · 18 tasks
  • 1.Inspect crankshaft vibration damper; inspect engine mounts; determine needed action.
  • 2.Remove, inspect, service, and install pans, covers, gaskets, seals, wear rings, and crankcase ventilation components; determine needed action.
  • 3.Perform crankcase pressure test; determine needed action.
  • 4.Install and align flywheel housing; inspect flywheel housing(s) to transmission housing/engine mating surface(s); and measure flywheel housing face and bore runout; determine needed action.
  • 5.Inspect flywheel/flexplate (including ring gear) and mounting surfaces for cracks and wear; measure runout; determine needed action.
  • 6.Disassemble and clean engine block; inspect engine block for cracks/damage; measure mating surfaces for warpage; check condition of passages, core/expansion plugs, and gallery plugs; inspect threaded holes, studs, dowel pins, and bolts for serviceability; determine needed action.
  • 7.Inspect cylinder sleeve counter bore and lower bore; check bore distortion; determine needed action.
  • 8.Clean, inspect, and measure cylinder walls or liners for wear and damage; determine needed action.
  • 9.Replace/reinstall cylinder liners and seals; check and adjust liner height (protrusion).
  • 10.Inspect camshaft bearings for wear and damage; determine needed action.
  • 11.Inspect, measure, and replace/reinstall camshaft; measure end play and backlash; determine needed action.
  • 12.Clean and inspect crankshaft for surface cracks and journal damage; check condition of oil passages; check passage plugs; measure journal diameter; determine needed action.
  • 13.Inspect main bearings for wear patterns and damage; replace as needed; check bearing clearances; check and correct crankshaft end play.
  • 14.Inspect, install, and time gear train; measure gear backlash; determine needed action.
  • 15.Inspect connecting rod and bearings for wear patterns; measure pistons, pins, retainers, and bushings; determine needed action.
  • 16.Determine piston-to-cylinder wall clearance; check ring-to-groove fit and end gap; install rings on pistons.
  • 17.Assemble pistons and connecting rods; install in block; install rod bearings and check clearances.
  • 18.Check condition of piston cooling jets (nozzles); determine needed action.
DLubrication System4 questions · 7 tasks
  • 1.Test engine oil pressure; check operation of pressure sensor, gauge, and/or sending unit; test engine oil temperature; check operation of temperature sensor; determine needed action.
  • 2.Check engine oil level, condition, and consumption; take engine oil sample; determine needed action.
  • 3.Determine proper lubricant; perform oil and filter service.
  • 4.Inspect, clean, and test oil cooler and components; determine needed action.
  • 5.Inspect turbocharger lubrication systems; determine needed action.
  • 6.Inspect and measure oil pump, drives, inlet pipes, and pick-up screens; check drive gear clearances; determine needed action.
  • 7.Inspect oil pressure regulator valve(s), by-pass and pressure relief valve(s), oil thermostat, and filters; determine needed action.
ECooling System7 questions · 12 tasks
  • 1.Check engine coolant type, level, and condition; test coolant for freeze protection and additive package concentration.
  • 2.Test coolant temperature; test operation of temperature and level sensors, gauge, and/or sending unit; determine needed action.
  • 3.Inspect and reinstall/replace pulleys, tensioners and drive belts; adjust drive belts and check alignment.
  • 4.Recover coolant; flush and refill with recommended coolant/additive package; bleed cooling system.
  • 5.Inspect coolant conditioner/filter assembly for leaks; inspect valves, lines, and fittings; replace as needed.
  • 6.Inspect water pump, hoses, and clamps; determine needed action.
  • 7.Inspect and pressure test cooling system(s); pressure test cap, tank(s), and recovery systems; inspect radiator and mountings; determine needed action.
  • 8.Inspect, test, and repair thermostatic cooling fan system (hydraulic, pneumatic, and electronic) and fan shroud; determine needed action.
  • 9.Test engine block heater(s); determine needed action.
  • 10.Diagnose engine coolant consumption; determine needed action.
  • 11.Inspect thermostat(s), by-passes, housing(s), and seals; replace as needed.
  • 12.Inspect turbocharger cooling systems; determine needed action.
FAir Induction, Exhaust Systems, and Engine Brakes7 questions · 16 tasks
  • 1.Inspect turbocharger(s), wastegate(s), and piping systems; determine needed action
  • 2.Diagnose air induction system problems; inspect, clean, and/or replace cooler assembly, piping, hoses, clamps, and mountings; replace air filter as needed; reset restriction indicator (if applicable).
  • 3.Inspect intake manifold, gaskets, and connections; determine needed action.
  • 4.Inspect engine exhaust system, exhaust gas recirculation (EGR) system, and exhaust aftertreatment system for leaks, mounting, proper routing, and damaged or missing components; determine needed action.
  • 5.Inspect crankcase ventilation system; service as needed.
  • 6.Diagnose problems/faults in the exhaust gas recirculation (EGR) system including: EGR valve, cooler, piping, filter, electronic sensors, controls, and wiring; determine needed action.
  • 7.Perform air intake system restriction and leakage tests; determine needed action.
  • 8.Perform intake manifold pressure (boost) test; determine needed action.
  • 9.Check exhaust back pressure; determine needed action.
  • 10.Inspect variable ratio geometry turbocharger (VGT), controls, and actuators (pneumatic, hydraulic, and electronic); determine needed action.
  • 11.Demonstrate knowledge of charge air cooler operation and testing.
  • 12.Diagnose exhaust aftertreatment system performance problems; determine needed action.
  • 13.Diagnose preheater/inlet air heater or glow plug system and controls: determine needed action.
  • 14.Inspect engine compression and/or exhaust brake housing, valves, seals, lines, and fittings; determine needed action.
  • 15.Inspect and adjust engine compression and/or exhaust brake systems; determine needed action.
  • 16.Inspect, test, and adjust engine compression and/or exhaust brake control circuits, switches, and solenoids; determine needed action.
GFuel System8 questions · 9 tasks
  • 1.Check fuel level and condition; determine needed action.
  • 2.Inspect fuel tanks, vents, caps, mounts, valves, screens, crossover system, hoses, lines, and fittings; determine needed action.
  • 3.Inspect low pressure fuel system components (fuel pump, pump drives, screens, fuel/water separators/indicators, hoses, lines, filters, heaters, coolers, ECM cooling plates, check valves, pressure regulator valves, restrictive fittings, and mounting hardware); determine needed action.
  • 4.Replace fuel filter; prime and bleed fuel system.
  • 5.Inspect high pressure fuel system components (fuel pump, pump drives, hoses, injection lines, filters, hold-downs, fittings, seals, and mounting hardware).
  • 6.Demonstrate knowledge and understanding of the different types of fuel systems.
  • 7.Perform fuel supply and return system tests; determine needed action.
  • 8.Perform cylinder contribution test using electronic service tool(s).
  • 9.Demonstrate knowledge of how to set performance parameters using electronic service tools and service information system access.

From the ASE Test Specifications and Task Lists, M/H Truck Series (2024), read October 20, 2026, in ASE's words. ASE's study guides page has the current PDF. Task lists for 43 ASE tests →

High-yield ASE Entry-Level Diesel Engines topics

The material that shows up year after year. If you're short on time, start here.

  • Fuel system: the safe way to find a leak at a high pressure fuel line or fitting is a piece of cardboard, with eye protection. High pressure fuel can go through skin, so never run a bare hand along the line.
  • Fuel supply testing: a vacuum gauge on the suction side reads restriction between the tank and the lift pump. High vacuum points to a plugged filter, kinked line or restricted pickup. Air bubbles in a clear test hose show air getting in.
  • Fuel system types: a unit injector combines the pump and nozzle in one assembly. A common rail system holds fuel at high pressure in a shared rail, and the ECM opens each injector. A HEUI injector uses high pressure engine oil on an intensifier piston.
  • Cooling system: use a refractometer or test strips to check freeze protection and coolant condition, not color or smell. Mix concentrate with distilled or deionized water, and let the engine cool and relieve pressure before you open the cap.
  • Air induction: a restricted air filter gives black smoke and low power. A leak in the charge-air piping or intake manifold gasket gives low boost and low power. Boost is read at the intake manifold, and intake restriction is read in the piping just before the turbo inlet.
  • General diagnosis: a single-cylinder misfire points to something specific to that cylinder, such as its injector. A problem on every cylinder points to something shared, like the fuel filter or air filter. A cylinder contribution test runs from the electronic service tool and tells you which cylinder is weak, not why.

Where techs lose points on ASE Entry-Level Diesel Engines

Good technicians miss these — not from lack of skill, but because the question is built to catch them.

  • Wrong belief: clearing a diagnostic code fixes the fault. Clearing only erases the record. Record active and inactive codes first, then repair the cause.
  • Wrong belief: white smoke and a dropping coolant level with no visible leak mean nothing serious. That pattern points to coolant entering a cylinder, such as a leaking head gasket. A block test can detect combustion gases in the coolant.
  • Wrong belief: low dash oil pressure always means worn bearings. A bad sender, wiring or gauge can show low pressure on a healthy engine. Check with a mechanical gauge at the engine's test port first.
  • Wrong belief: a bent push rod can be straightened, or a cracked head or flywheel can be reused. Bent push rods are replaced. A cracked cylinder head must be repaired or replaced, and a cracked flywheel is replaced.

A study plan that works for ASE Entry-Level Diesel Engines

Roughly two weeks of real preparation, in the order that actually builds on itself.

  1. Day 1: Fuel system, the biggest area at 8 questions. Cover tank, vent, crossover, filters, priming, high pressure safety, fuel types, and supply tests with a vacuum gauge.
  2. Day 2: Cooling system and air induction, 7 questions each. Cover coolant testing, belts, water pump weep holes, pressure tests, thermostats, turbo and wastegate, boost, back pressure, EGR and engine brakes.
  3. Day 3: General diagnosis, 7 questions. Cover service information and TSBs, smoke colors, no-start and low-power causes, scan tool codes, and meter readings.
  4. Day 4: Cylinder head, lubrication and block, 11 questions together. Cover which tool measures what, oil pressure and oil sample checks, then take a full practice test and review every miss.

Sample ASE Entry-Level Diesel Engines questions

Straight from the bank — answers highlighted, with the explanation underneath.

Which is the BEST source for the correct engine oil specification for a particular diesel engine?

  1. The brand name on the oil drum the shop stocks
  2. The color of the used oil in the pan
  3. The engine manufacturer's service information
  4. The oil level shown on the dipstick
WhyThe engine manufacturer publishes the required oil viscosity and performance category for each engine in its service information. Using that specification protects the engine and any warranty. Shop habit or the look of the oil does not tell you what the engine requires.

A technician finds an engine wiring harness rubbing on a bracket edge with the insulation worn through. What is the correct action?

  1. Tighten the connector retainers
  2. Wrap tape over it and leave it routed there
  3. Leave it if the engine runs normally
  4. Repair the wires and reroute the harness
WhyWorn insulation can short or open a circuit. The wires must be repaired and the harness rerouted and secured so it no longer rubs.

Which finding on a crankshaft vibration damper requires replacement?

  1. Light dust on the outer ring
  2. Index marks shifted out of alignment
  3. Clean paint on the outer ring
  4. Normal belt marks in the groove
WhyShifted index marks mean the damper's outer ring or rubber has slipped, so it no longer controls crankshaft torsional vibration. Dents, leaks, and cracked rubber are also replacement items.

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