Quiz 1 - Engine Design And Testing
Review questions on engine design
Questions and Answers
- 1.
The_____stroke has the piston moving up and down and squeezing the air/fuel mixture in the cylinder.
- A.
Intake
- B.
Compression
- C.
Power
- D.
Exhaust
Correct Answer
B. CompressionExplanation
The compression stroke is the correct answer because during this stroke, the piston moves upward, compressing the air/fuel mixture in the cylinder. This compression increases the pressure and temperature of the mixture, preparing it for ignition and combustion in the power stroke.Rate this question:
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- 2.
The_____stroke has the piston moving down after the air /fuel mixture explodes in the cylinder.
- A.
Intake
- B.
Compression
- C.
Power
- D.
Exhaust
Correct Answer
C. PowerExplanation
The power stroke is the correct answer because it is the stage in the four-stroke combustion cycle where the piston moves down after the air/fuel mixture explodes in the cylinder. During this stroke, the expanding gases from the combustion push the piston downward, generating power that is used to turn the crankshaft and ultimately propel the vehicle.Rate this question:
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- 3.
The_____stroke has the piston moving down and an air / fuel mixture entering the cylinder.
- A.
Intake
- B.
Compression
- C.
Power
- D.
Exhaust
Correct Answer
A. IntakeExplanation
During the intake stroke, the piston moves downward, creating space in the cylinder. This allows the air/fuel mixture to be drawn into the cylinder through the intake valve. This process is crucial for the internal combustion engine as it prepares the mixture for combustion in the subsequent strokes.Rate this question:
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- 4.
The_____stroke has the piston moving up and forcing the burnt air / fuel mixture out of the cylinder.
- A.
Intake
- B.
Compression
- C.
Power
- D.
Exhaust
Correct Answer
D. ExhaustExplanation
The exhaust stroke is the correct answer because during this stroke, the piston moves up, pushing the burnt air/fuel mixture out of the cylinder. This stroke occurs after the power stroke, where the fuel is ignited and the piston is forced down, generating power. The exhaust stroke completes the four-stroke combustion cycle in an internal combustion engine.Rate this question:
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- 5.
Manifold vacuum is formed on the piston's_____stroke.
- A.
Intake
- B.
Compression
- C.
Power
- D.
Exhaust
Correct Answer
A. IntakeExplanation
During the intake stroke, the piston moves downward, creating a vacuum in the cylinder. This vacuum allows the intake valve to open, allowing the air-fuel mixture to enter the combustion chamber. The formation of manifold vacuum during the intake stroke is crucial for the engine's operation as it helps in drawing in the necessary air-fuel mixture for combustion.Rate this question:
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- 6.
Which one of the following is not a stroke of the four-stroke cycle?
- A.
Intake
- B.
Compression
- C.
Ignition
- D.
Exhaust
Correct Answer
C. IgnitionExplanation
The four-stroke cycle is a series of steps that occur in an internal combustion engine. It includes the intake stroke, compression stroke, power stroke (or ignition), and exhaust stroke. The intake stroke involves the intake valve opening and the piston moving downward to allow a fuel-air mixture into the combustion chamber. The compression stroke involves the piston moving upward, compressing the fuel-air mixture. The power stroke (or ignition) involves the spark plug igniting the compressed fuel-air mixture, causing an explosion and pushing the piston downward. Finally, the exhaust stroke involves the piston moving upward again, pushing out the burned gases through the exhaust valve. Therefore, ignition is not a stroke of the four-stroke cycle.Rate this question:
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- 7.
A four-stroke cycle engine requires at least___valves at the top of each cylinder.
- A.
One
- B.
Two
- C.
Three
- D.
Four
Correct Answer
B. TwoExplanation
A four-stroke cycle engine requires at least two valves at the top of each cylinder. This is because the four-stroke cycle includes intake, compression, power, and exhaust strokes. The intake stroke requires the intake valve to open to allow the air-fuel mixture into the cylinder, while the exhaust stroke requires the exhaust valve to open to release the burnt gases. Therefore, a minimum of two valves is needed to facilitate these processes efficiently.Rate this question:
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- 8.
Technician A says an engine's firing order is always the same as the cylinder numbering on the crankshaft. Technician B says an engine's firing order is the order in which the cylinders' spark plugs fire. Who is correct?
- A.
A only
- B.
B only
- C.
Both A and B
- D.
Neither A nor B
Correct Answer
B. B onlyExplanation
Technician B is correct. The firing order of an engine refers to the specific sequence in which each cylinder's spark plug fires. This sequence is determined by the engine's design and is not necessarily the same as the cylinder numbering on the crankshaft. Therefore, Technician A's statement is incorrect.Rate this question:
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- 9.
Which of the following conditions is generally not revealed by vacuum readings?
- A.
Restricted exhaust system
- B.
Uneven compression
- C.
Weak ignition spark
- D.
Vacuum leak
Correct Answer
C. Weak ignition sparkExplanation
Vacuum readings are used to diagnose various engine problems by measuring the level of vacuum in the intake manifold. They can reveal conditions such as a restricted exhaust system, uneven compression, and vacuum leaks. However, a weak ignition spark is generally not revealed by vacuum readings. Weak ignition spark can be caused by issues such as faulty spark plugs, ignition coils, or ignition timing. To diagnose a weak ignition spark, other methods such as checking the spark plugs or using a spark tester would be more appropriate.Rate this question:
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- 10.
Vacuum readings of_____and a steady reading are considered acceptable for most engines running at idle speed.
- A.
2 to 5 inches
- B.
At least 100 psi
- C.
15 to 22 inches
- D.
No more than 20%
Correct Answer
C. 15 to 22 inchesExplanation
Vacuum readings of 15 to 22 inches and a steady reading are considered acceptable for most engines running at idle speed. This means that the engine is producing enough vacuum pressure to operate efficiently. Vacuum readings outside of this range may indicate potential issues with the engine's performance or mechanical problems.Rate this question:
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- 11.
When testing for an exhaust restriction, Technician A runs the engine for a minute at about 2000 rpm with a vacuum gauge installed. Technician B says that a steady reading for the full minute of the test run by Technician A indicates an exhaust restriction. Who is correct?
- A.
A only
- B.
B only
- C.
Both A and B
- D.
Neither A nor B
Correct Answer
D. Neither A nor BExplanation
Neither Technician A nor Technician B is correct. A steady reading on the vacuum gauge during the test run does not necessarily indicate an exhaust restriction. Other factors, such as the condition of the engine or the gauge itself, could affect the reading. To accurately determine if there is an exhaust restriction, additional tests and diagnostics would be necessary.Rate this question:
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- 12.
Compression readings of_____ and all cylinders within 25% are considered acceptable for most engines.
- A.
2 to 5 inches
- B.
At least 100 psi
- C.
15 to 22 inches
- D.
No more than 20%
Correct Answer
B. At least 100 psiExplanation
Compression readings of at least 100 psi are considered acceptable for most engines. This means that the pressure within each cylinder should be at least 100 pounds per square inch. Compression readings below this threshold may indicate a problem with the engine, such as worn piston rings or valves. Therefore, it is important to ensure that the compression readings are at least 100 psi to ensure the engine's proper functioning.Rate this question:
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- 13.
When wet compression test readings are considerably higher than dry compression test readings, what situation is most likely indicated?
- A.
The engine has leaking valves
- B.
The engine test results are normal
- C.
The engine has worn piston rings
- D.
The engine has a worn camshaft
Correct Answer
C. The engine has worn piston ringsExplanation
When wet compression test readings are considerably higher than dry compression test readings, it indicates that the engine has worn piston rings. The wet compression test involves adding a small amount of oil to the cylinder, which helps to seal the piston rings and temporarily increase compression. If the wet compression readings are significantly higher than the dry compression readings, it suggests that the piston rings are not sealing properly, allowing oil to enter the combustion chamber and improve compression. This indicates that the piston rings are worn and need to be replaced.Rate this question:
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- 14.
Cylinder leakage readings of_____ with the only leakage past the piston rings are considered acceptable for most engines.
- A.
2 to 5 inches
- B.
At least 100 psi
- C.
15 to 22 inches
- D.
No more than 20%
Correct Answer
D. No more than 20%Explanation
Cylinder leakage readings of no more than 20% with the only leakage past the piston rings are considered acceptable for most engines. This means that if the amount of leakage past the piston rings is within this range, it is considered normal and does not indicate any major issues with the engine.Rate this question:
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- 15.
When conducting a cylinder leakage test, Technician A says 15 percent leakage around the rings mean the cylinder in question is defective. Technician B says 15 percent leakage past the intake valve is considered acceptable. Who is correct?
- A.
A only
- B.
B only
- C.
Both A and B
- D.
Neither A nor B
Correct Answer
D. Neither A nor BExplanation
Technician A is incorrect because 15 percent leakage around the rings does not necessarily mean the cylinder is defective. It could be caused by other factors such as worn piston rings or cylinder wall damage. Technician B is also incorrect because 15 percent leakage past the intake valve is not considered acceptable. Any leakage past the intake valve indicates a problem with the valve or valve seat. Therefore, neither Technician A nor Technician B is correct.Rate this question:
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- 16.
Which of the following engine problems may be indicated by good results from a cylinder leakage test but poor results from a running vacuum test at idle and poor results from a compression test.
- A.
Intake valve not opening
- B.
Leaking head gasket
- C.
Leaking intake valve
- D.
Worn piston rings
Correct Answer
A. Intake valve not openingExplanation
If the cylinder leakage test results are good but the running vacuum test at idle and the compression test results are poor, it suggests that there is a problem with the intake valve not opening. This means that the intake valve is not allowing the proper amount of air and fuel mixture into the cylinder, resulting in poor engine performance. The leakage test may not detect this issue as it focuses on other potential problems such as leaks in the cylinder or piston rings.Rate this question:
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- 17.
What is a 'universal' first step in most engine testing?
- A.
Disable the ignition system
- B.
Hold the throttle wide open
- C.
Charge the battery
- D.
Warm up the engine if possible
Correct Answer
D. Warm up the engine if possibleExplanation
In most engine testing, warming up the engine is considered a universal first step. This is because warming up the engine helps to ensure proper lubrication and circulation of fluids, as well as allowing the engine to reach its optimal operating temperature. By warming up the engine, any potential issues or abnormalities can be identified before putting the engine under load or stress during testing. Therefore, warming up the engine is an essential step in engine testing to ensure accurate and reliable results.Rate this question:
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- 18.
What is considered the best way to determine if there is a head gasket leaking between a combustion chamber and the cooling system?
- A.
Vacuum test
- B.
Compression test
- C.
Cylinder leakage test
- D.
Test the cooling system for combustion gasses (chemical or exhaust analyzer)
Correct Answer
D. Test the cooling system for combustion gasses (chemical or exhaust analyzer)Explanation
The best way to determine if there is a head gasket leaking between a combustion chamber and the cooling system is to test the cooling system for combustion gases using a chemical or exhaust analyzer. This method allows for the detection of any gases that may have leaked from the combustion chamber into the cooling system, indicating a head gasket leak. Vacuum test, compression test, and cylinder leakage test may be useful in diagnosing other engine problems, but they are not specifically designed to detect head gasket leaks in the cooling system.Rate this question:
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- 19.
Which test can give you the best idea of which cylinder has a problem and in most cases what specific problem exists in that cylinder?
- A.
Vacuum test
- B.
Compression test
- C.
Cylinder leakage test
- D.
Lubricating system gas analysis
Correct Answer
C. Cylinder leakage testExplanation
The cylinder leakage test is the best test to determine which cylinder has a problem and identify the specific problem in most cases. This test measures the amount of pressure leakage in each cylinder, which can help identify issues such as worn piston rings, damaged valves, or a blown head gasket. By comparing the leakage values of each cylinder, the test can pinpoint the specific cylinder that is experiencing problems and provide valuable information for diagnosis and repair.Rate this question:
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- 20.
Which of the following can under certain conditions sound like an internal engine ticking noise?
- A.
Normal fuel injector noise
- B.
Minor exhaust leaks near the engine
- C.
Certain emission control devices cycling on and off
- D.
All of the above
Correct Answer
D. All of the aboveExplanation
Under certain conditions, all of the given options can sound like an internal engine ticking noise. Normal fuel injector noise can create a ticking sound, especially if the injectors are dirty or clogged. Minor exhaust leaks near the engine can also produce a ticking noise as the exhaust gases escape through the small gaps. Additionally, certain emission control devices cycling on and off, such as the EGR valve or PCV valve, can cause a ticking sound. Therefore, all of these factors can contribute to an internal engine ticking noise.Rate this question:
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