• 45 questions

ASE A1 Study Guide

Unofficial engine repair practice in the five content areas of ASE's A1 test specifications, every answer with its source.

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How is the throttle held while the engine is cranked for a compression test?

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Unofficial practice questions, not affiliated with the National Institute for Automotive Service Excellence (ASE). Bank checked October 8, 2026.

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All 45 questions with answers

General engine diagnosis 18

  • A cylinder reads low on a compression test. A tablespoon of heavy oil is poured in through the plug hole and the reading rises to near normal. Where is the compression being lost? Answer: Past the piston rings. Source: U.S. Navy, Construction Mechanic Advanced (NAVEDTRA 14050, 1992), chapter 3, Compression Test. ASE A1 content area A, General Engine Diagnosis (18 of 45 questions)
  • A heavy, dull, regular knock is heard only under load or on acceleration. What is the most likely source? Answer: Worn main bearings. Source: U.S. Navy, Construction Mechanic Advanced (NAVEDTRA 14050, 1992), chapter 3, Crankshaft Knock. ASE A1 content area A, General Engine Diagnosis (18 of 45 questions)
  • A light knock is loudest as the throttle is eased off at medium speed. Shorting out one cylinder makes it much quieter. Which part is the likely source? Answer: A connecting rod bearing. Source: U.S. Navy, Construction Mechanic Advanced (NAVEDTRA 14050, 1992), chapter 3, Connecting Rod Noise. ASE A1 content area A, General Engine Diagnosis (18 of 45 questions)
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General engine diagnosis, continued

  • A low cylinder is retested with oil added and the compression reading does not change. What does that point to? Answer: Leakage past the valves. Source: U.S. Navy, Construction Mechanic Advanced (NAVEDTRA 14050, 1992), chapter 3, Compression Test. ASE A1 content area A, General Engine Diagnosis (18 of 45 questions)
  • A sound engine idles at an elevation under 1,000 feet. What should a vacuum gauge on the intake manifold show? Answer: A steady 17 to 22 inches. Source: U.S. Navy, Construction Mechanic Advanced (NAVEDTRA 14050, 1992), chapter 3, Vacuum Gauge Test. ASE A1 content area A, General Engine Diagnosis (18 of 45 questions)
  • An engine with a leaking head gasket sat overnight. Now it will not turn at all on the starter, though the battery and starter test good. What should be suspected before forcing it? Answer: A cylinder filled with liquid. Source: Wikipedia, Hydrolock, section Symptoms and damage. ASE A1 content area A, General Engine Diagnosis (18 of 45 questions)
  • An intake manifold gasket is leaking air. What would a vacuum gauge show at idle? Answer: A steady low reading. Source: U.S. Navy, Construction Mechanic Advanced (NAVEDTRA 14050, 1992), chapter 3, Vacuum Gauge Test. ASE A1 content area A, General Engine Diagnosis (18 of 45 questions)
  • As the engine is accelerated, the vacuum gauge pointer swings widely. Which fault fits that reading? Answer: A weak valve spring. Source: U.S. Navy, Construction Mechanic Advanced (NAVEDTRA 14050, 1992), chapter 3, Vacuum Gauge Test. ASE A1 content area A, General Engine Diagnosis (18 of 45 questions)
  • At idle the vacuum gauge pointer sits at a steady 10 inches. What does the Navy manual say this usually means? Answer: Valve timing is incorrect. Source: U.S. Navy, Construction Mechanic Advanced (NAVEDTRA 14050, 1992), chapter 3, Vacuum Gauge Test. ASE A1 content area A, General Engine Diagnosis (18 of 45 questions)
  • Coolant level keeps dropping with no outside leak, and steam (white smoke) shows at the tailpipe. What is the most likely cause? Answer: A leaking head gasket. Source: Wikipedia, Head gasket, section Coolant leakage. ASE A1 content area A, General Engine Diagnosis (18 of 45 questions)
  • During a compression test one cylinder is low for the first few strokes, then climbs to near normal. What is indicated? Answer: A sticking valve. Source: U.S. Navy, Construction Mechanic Advanced (NAVEDTRA 14050, 1992), chapter 3, Compression Test. ASE A1 content area A, General Engine Diagnosis (18 of 45 questions)
  • During a cylinder leakage test, air is heard rushing out of the oil filler opening. Where is the cylinder leaking? Answer: Past the piston rings. Source: U.S. Navy, Construction Mechanic Advanced (NAVEDTRA 14050, 1992), chapter 3, Cylinder Leakage Test. ASE A1 content area A, General Engine Diagnosis (18 of 45 questions)
  • During a cylinder leakage test, bubbles rise in the coolant at the radiator filler. What is leaking? Answer: The head gasket. Source: U.S. Navy, Construction Mechanic Advanced (NAVEDTRA 14050, 1992), chapter 3, Cylinder Leakage Test. ASE A1 content area A, General Engine Diagnosis (18 of 45 questions)
  • The exhaust has a bluish tinge and the oil level keeps falling, with no outside leaks. What is happening? Answer: Oil is burning in the combustion chamber. Source: U.S. Navy, Construction Mechanic Advanced (NAVEDTRA 14050, 1992), chapter 3, Excessive Oil Consumption. ASE A1 content area A, General Engine Diagnosis (18 of 45 questions)
  • How is the throttle held while the engine is cranked for a compression test? Answer: Wide open. Source: U.S. Navy, Construction Mechanic Advanced (NAVEDTRA 14050, 1992), chapter 3, Compression Test. ASE A1 content area A, General Engine Diagnosis (18 of 45 questions)
  • Two cylinders that sit side by side both read low on a compression test. Every other cylinder is normal. What is the most likely cause? Answer: A blown head gasket. Source: U.S. Navy, Construction Mechanic Advanced (NAVEDTRA 14050, 1992), chapter 3, Compression Test. ASE A1 content area A, General Engine Diagnosis (18 of 45 questions)
  • Under heavy load, manifold vacuum is low and blowby is at its highest. What does the PCV valve do? Answer: Opens fully. Source: U.S. Army TM 9-8000, Principles of Automotive Vehicles (1985), paragraph 7-7b, Positive Crankcase Ventilation System. ASE A1 content area A, General Engine Diagnosis (18 of 45 questions)
  • Where is the piston placed before shop air is fed into a cylinder for a leakage test? Answer: TDC, between compression and power. Source: U.S. Navy, Construction Mechanic Advanced (NAVEDTRA 14050, 1992), chapter 3, Cylinder Leakage Test. ASE A1 content area A, General Engine Diagnosis (18 of 45 questions)

Cylinder head and valve train 6

  • A timing belt breaks on an interference engine. Which check can find bent valves before the head comes off? Answer: A cylinder leak-down test. Source: Wikipedia, Interference engine, section Timing gear failure. ASE A1 content area B, Cylinder Head and Valve Train Diagnosis and Repair (6 of 45)
  • After refacing, a valve cannot keep the specified margin. What is done with the valve? Answer: It is discarded. Source: U.S. Navy, Construction Mechanic Advanced (NAVEDTRA 14050, 1992), chapter 3, Valve Grinding. ASE A1 content area B, Cylinder Head and Valve Train Diagnosis and Repair (6 of 45)
  • Some engines call for the valve face to be ground about 1/4 to 1 degree flatter than the seat. What is this difference called? Answer: An interference angle. Source: U.S. Navy, Construction Mechanic Advanced (NAVEDTRA 14050, 1992), chapter 3, Valve Grinding. ASE A1 content area B, Cylinder Head and Valve Train Diagnosis and Repair (6 of 45)
  • The springs are off and a valve is held just off its seat. A dial indicator touches the edge of the valve head while the head is moved sideways. What is being measured? Answer: Valve guide wear. Source: U.S. Navy, Construction Mechanic Advanced (NAVEDTRA 14050, 1992), chapter 3, Valve Guide Servicing. ASE A1 content area B, Cylinder Head and Valve Train Diagnosis and Repair (6 of 45)
  • What are valve spring shims properly used for? Answer: Setting installed spring height. Source: U.S. Navy, Construction Mechanic Advanced (NAVEDTRA 14050, 1992), chapter 3, Valve Spring Testing. ASE A1 content area B, Cylinder Head and Valve Train Diagnosis and Repair (6 of 45)
  • What happens to valves that are adjusted with too little clearance? Answer: They overheat and warp. Source: U.S. Navy, Construction Mechanic Advanced (NAVEDTRA 14050, 1992), chapter 3, Valve Adjustments. ASE A1 content area B, Cylinder Head and Valve Train Diagnosis and Repair (6 of 45)

Engine block 4

  • A cylinder is worn tapered. Where in the bore is a new piston ring fitted for end gap? Answer: At the lower limit of ring travel. Source: U.S. Navy, Construction Mechanic Advanced (NAVEDTRA 14050, 1992), chapter 3, Piston Rings Fitting. ASE A1 content area C, Engine Block Diagnosis and Repair (4 of 45)
  • A strip of plastic gauging material is clamped between a main bearing and its journal to check the clearance. What must not be done until the cap is off again? Answer: Turn the crankshaft. Source: U.S. Navy, Construction Mechanic Advanced (NAVEDTRA 14050, 1992), chapter 3, Checking of Bearing Fit. ASE A1 content area C, Engine Block Diagnosis and Repair (4 of 45)
  • Micrometer readings taken at several points around one crankshaft journal differ from each other. What does that show? Answer: The journal is out of round. Source: U.S. Navy, Construction Mechanic Advanced (NAVEDTRA 14050, 1992), chapter 3, Crankshaft Journal Check. ASE A1 content area C, Engine Block Diagnosis and Repair (4 of 45)
  • Pistons are to be pushed out through the top of a worn block. What is removed from each cylinder first? Answer: The cylinder ridge. Source: U.S. Navy, Construction Mechanic Advanced (NAVEDTRA 14050, 1992), chapter 3, Pistons and Rings Servicing. ASE A1 content area C, Engine Block Diagnosis and Repair (4 of 45)

Lubrication and cooling 8

  • A freshly overhauled engine is started and the gauge shows no oil pressure. Within what time does the Navy manual say to shut it down? Answer: 10 to 15 seconds. Source: U.S. Navy, Construction Mechanic Advanced (NAVEDTRA 14050, 1992), chapter 3, Initial Start-up and Run-in. ASE A1 content area D, Lubrication and Cooling Systems Diagnosis and Repair (8 of 45)
  • An engine takes far too long to warm up and its oil smells of fuel. Which cooling system part is the first suspect? Answer: The thermostat. Source: U.S. Army TM 9-8000, Principles of Automotive Vehicles (1985), paragraph 9-9a, Thermostats. ASE A1 content area D, Lubrication and Cooling Systems Diagnosis and Repair (8 of 45)
  • As the engine cools down, which part of the radiator pressure cap opens so that the hoses do not collapse? Answer: The vacuum valve. Source: U.S. Army TM 9-8000, Principles of Automotive Vehicles (1985), paragraph 9-10b, Radiator Pressure Cap. ASE A1 content area D, Lubrication and Cooling Systems Diagnosis and Repair (8 of 45)
  • In a full-flow oil system, what keeps oil reaching the bearings when the filter element clogs? Answer: A bypass valve in the filter. Source: U.S. Army TM 9-8000, Principles of Automotive Vehicles (1985), paragraph 8-13d, Filter System Configurations. ASE A1 content area D, Lubrication and Cooling Systems Diagnosis and Repair (8 of 45)
  • Oil pressure is low on a high-mileage engine that has the right oil at the right level. What does this often indicate? Answer: Worn engine bearings. Source: U.S. Navy, Construction Mechanic Advanced (NAVEDTRA 14050, 1992), chapter 3, Low Oil Pressure. ASE A1 content area D, Lubrication and Cooling Systems Diagnosis and Repair (8 of 45)
  • What does the oil pressure regulator valve do when pump pressure reaches the value set by its spring? Answer: Opens and returns excess oil to the crankcase. Source: U.S. Army TM 9-8000, Principles of Automotive Vehicles (1985), paragraph 8-16, Pressure Regulator. ASE A1 content area D, Lubrication and Cooling Systems Diagnosis and Repair (8 of 45)
  • What happens to freeze protection when the share of ethylene glycol is raised well above 60 percent? Answer: It gets worse: the freezing point rises. Source: U.S. Army TM 9-8000, Principles of Automotive Vehicles (1985), paragraph 9-5a, Antifreeze Protection. ASE A1 content area D, Lubrication and Cooling Systems Diagnosis and Repair (8 of 45)
  • When does a viscous fan clutch let the fan slip? Answer: When air through the radiator is below a set temperature. Source: U.S. Army TM 9-8000, Principles of Automotive Vehicles (1985), paragraph 9-8a, Thermostatically Controlled Engine-Driven Fan. ASE A1 content area D, Lubrication and Cooling Systems Diagnosis and Repair (8 of 45)

Fuel, electrical, ignition, air and exhaust 9

  • A battery has six cells in series. What is its voltage at full charge, at rest? Answer: 12.6 volts. Source: Wikipedia, Automotive battery, opening section. ASE A1 content area E, Fuel, Electrical, Ignition, Air Induction and Exhaust Systems Diagnosis and Service (9 of 45)
  • A crushed exhaust pipe raises back pressure. What is the effect on the engine? Answer: Power output falls. Source: Wikipedia, Back pressure, section Explanation. ASE A1 content area E, Fuel, Electrical, Ignition, Air Induction and Exhaust Systems Diagnosis and Service (9 of 45)
  • A spark plug has misfired for weeks. Besides raw fuel in the exhaust, what happens in the crankcase? Answer: Unburned fuel passes the rings and thins the oil. Source: U.S. Army TM 9-8000, Principles of Automotive Vehicles (1985), paragraph 8-4c, Oil Dilution. ASE A1 content area E, Fuel, Electrical, Ignition, Air Induction and Exhaust Systems Diagnosis and Service (9 of 45)
  • An intake duct is cracked between the air filter and the throttle body. What is the mechanical risk to the engine? Answer: Dirt is drawn in and causes internal damage. Source: U.S. Navy, Construction Mechanic Advanced (NAVEDTRA 14050, 1992), chapter 5, Servicing and Precautions. ASE A1 content area E, Fuel, Electrical, Ignition, Air Induction and Exhaust Systems Diagnosis and Service (9 of 45)
  • Cranking voltage is high, yet the starter turns the engine sluggishly. What is checked next? Answer: Resistance in the starting circuit. Source: U.S. Navy, Construction Mechanic Advanced (NAVEDTRA 14050, 1992), chapter 4, Cranking Voltage Test. ASE A1 content area E, Fuel, Electrical, Ignition, Air Induction and Exhaust Systems Diagnosis and Service (9 of 45)
  • On a fuel-injected engine, air leaks into the intake manifold without being measured. What mixture reaches the cylinders? Answer: A lean mixture. Source: U.S. Navy, Construction Mechanic Advanced (NAVEDTRA 14050, 1992), chapter 5, Servicing and Precautions. ASE A1 content area E, Fuel, Electrical, Ignition, Air Induction and Exhaust Systems Diagnosis and Service (9 of 45)
  • One cylinder is burning oil. What does that tend to do to its spark plug? Answer: Foul the tip and inhibit the spark. Source: Wikipedia, Spark plug, section on tip protrusion and fouling. ASE A1 content area E, Fuel, Electrical, Ignition, Air Induction and Exhaust Systems Diagnosis and Service (9 of 45)
  • While the starter cranks the engine, a 12-volt system should hold at least what voltage, unless the maker specifies otherwise? Answer: 9.6 volts. Source: U.S. Navy, Construction Mechanic Advanced (NAVEDTRA 14050, 1992), chapter 4, Cranking Voltage Test. ASE A1 content area E, Fuel, Electrical, Ignition, Air Induction and Exhaust Systems Diagnosis and Service (9 of 45)
  • Why must replacement fuel line on a gasoline injection system be approved for that use? Answer: Injection pressure is up to five times higher. Source: U.S. Navy, Construction Mechanic Advanced (NAVEDTRA 14050, 1992), chapter 5, Servicing and Precautions, caution. ASE A1 content area E, Fuel, Electrical, Ignition, Air Induction and Exhaust Systems Diagnosis and Service (9 of 45)

How this list was compiled: Our own questions, written to the test specifications for Engine Repair (Test A1) in the ASE Automobile Study Guide (https://ase.com/wp-content/uploads/ASE_Automobile_Study_Guide.pdf, marked (c) ASE 2026, read 2026-10-08): A general engine diagnosis 18 questions, B cylinder head and valve train 6, C engine block 4, D lubrication and cooling systems 8, E fuel, electrical, ignition, air induction and exhaust systems 9; total 45. The bank holds the same 18, 6, 4, 8 and 9. Each fact was read on 2026-10-08 in the public source named under its question: the U.S. Navy training manual Construction Mechanic Advanced (NAVEDTRA 14050, 1992), the U.S. Army manual TM 9-8000 Principles of Automotive Vehicles (1985) and, for six questions, Wikipedia. Licence: Questions, choices and explanations are original work of this site.

How it works

This free ASE A1 study guide is a practice test: 45 engine repair questions of our own, weighted like the real test. It is unofficial and not affiliated with, endorsed by or sponsored by the National Institute for Automotive Service Excellence (ASE).

Read the full guide

What the A1 test covers

ASE's study guide splits the 45 scored questions, and this bank with them: general engine diagnosis 18, cylinder head and valve train 6, engine block 4, lubrication and cooling 8, and fuel, electrical, ignition, air induction and exhaust 9.

Length and timing

The real test allows 75 minutes for all 55 questions. Exam mode asks 45, the scored count, in the same 75 minutes.

The ASE A1 engine repair practice test as a guide

Each explanation names the manual and section it rests on, so a missed question tells you what to read.

  • General diagnosis is 40 percent of the test. Know what compression, vacuum and leak-down readings point to before the parts questions.
  • In each scenario, find the one thing that changed: oil added to a cylinder, a plug shorted out, the throttle opened.

Questions and answers

How many questions are on the ASE A1 test?

55 in all: ASE lists 45 scored questions and 10 that are not counted for score. You are not told which, so answer every one. The recertification test is 23 questions in 30 minutes.

Is there an ASE A1 study guide PDF?

Yes, and it is free: ASE publishes one study guide for tests A1 to A9, with the test specifications and the task list. This page follows that outline. For ASE A1 test prep on paper, print the paper test here.

Are these real A1 ASE test questions?

No. Every question is our own, written from ASE's task list and from public Navy and Army training manuals. None is taken from the ASE A1 test or from the sample questions in the guide, so a score here is practice only.

Does this ASE engine repair practice test cover the whole ASE A1 test study guide?

No. ASE's task list also names variable valve timing and lift, cylinder deactivation, electronically controlled thermostats and electric coolant pumps. This bank asks none of them, so read those tasks in the ASE engine repair study guide itself.

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