Question 1

Technician A says that it is acceptable practice to clean air filters by using compressed shop air. Technician B says it is better to clean air filters by dropping or lightly tapping the filter against the shop floor. Who is correct?

Accepted Answer

Using compressed air or tapping the filter can damage the filter material or fail to remove all debris, so neither method is recommended. It's best to replace air filters as needed.

Question 2

An engine had a fault code for high crankcase pressure, and its power is derated. Technician A says that the crankcase filter could have frozen when it was exposed to extreme cold conditions. Technician B says that a frozen filter would likely blow engine gaskets and seals rather than cause a derate condition. Who is correct?

Accepted Answer

Both Technician A and B are correct. A frozen crankcase filter can cause high crankcase pressure, and while it can lead to blown gaskets and seals, it can also cause the engine to derate as a protective measure.

Question 3

What is the primary use for a resonator box on the air inlet of a diesel engine?

Accepted Answer

The primary use of a resonator box on the air inlet of a diesel engine is to dampen intake noise, reducing the sound produced by the engine's air intake system.

Question 4

Technician A says that diesel engines use more air than gasoline-fueled engines because 1 gallon (3.7 liters) of diesel fuel requires more air to burn than the same amount of gasoline. Technician B says that a diesel engine uses more air to prevent pistons and valves from burning. Who is correct?

Accepted Answer

Diesel engines do require more air for combustion compared to gasoline engines, as diesel fuel has a higher energy content and requires more air for complete combustion. Additionally, the excess air helps in cooling the engine components, preventing pistons and valves from burning.

Question 5

Technician A says that a throttle plate on a late-model diesel engine helps increase the exhaust temperatures for the exhaust aftertreatment catalysts. Technician B says diesel air intake is not throttled. Who is correct?

Accepted Answer

The answer of Technician A says that a throttle plate...

Question 6

The service interval of an air filter is best determined by which of the following?

Accepted Answer

The measurement of air filter restriction is the most accurate way to determine the service interval, as it directly assesses the filter's ability to allow air flow, indicating when it needs replacement.

Question 7

Which air filter element will provide the highest filtration efficiency (i.e., which removes the most dirt)?

Accepted Answer

The answer of Which air filter element will provide the...

Question 8

Which of the following air intake systems will best pre-clean dirt and water from the air intake of an on-highway, diesel-powered vehicle?

Accepted Answer

Side-mounted air inlets are often designed to help pre-clean dirt and water from the air intake by utilizing the vehicle's body to shield the intake from direct exposure to road debris and water.

Question 9

Technician A says that the best practice is to replace air filters on turbocharged engines when the restriction gauge reads 20-25" (51-63 cm) of H₂O. Technician B says the filter should be replaced around 10-15" (25-38 cm) H₂O to prevent increased fuel consumption caused by a restricted air filter. Who is correct?

Accepted Answer

Technician B is correct because replacing the air filter at 10-15" (25-38 cm) H₂O helps prevent increased fuel consumption and ensures optimal engine performance.

Question 10

Technician A says that frequent air filter changes help maintain the cleanest quality of air that enters the engine. Technician B says that dirty filters are better than clean filters at allowing cleaner air to enter the engine. Who is correct?

Accepted Answer

The answer of Technician A says that frequent air filter...

Question 11

Technician A says that electric intake heaters are used to reduce cold-start and warm-up emissions. Technician B says that intake air heaters help to shorten the cranking time of a cold engine. Who is correct?

Accepted Answer

Both Technician A and Technician B are correct. Electric intake heaters are used to reduce cold-start and warm-up emissions by heating the air entering the engine, which helps in better fuel atomization and combustion. They also help to shorten the cranking time of a cold engine by providing warmer air, which aids in easier starting.

Question 12

Technician A says that crankcase coalescing filters are used to minimize particulate emissions from diesel engines. Technician B says that centrifugal separators of air and oil reduce engine oil consumption. Who is correct?

Accepted Answer

Crankcase coalescing filters help reduce particulate emissions by capturing oil mist and other particulates, while centrifugal separators help reduce engine oil consumption by separating oil from the air before it is vented out.

Question 13

Technician A says that a crankcase depression regulator is used to prevent overpressurizing an engine's crankcase. Technician B says that the crankcase depression regulator prevents dirt from entering the engine through seals and gaskets. Who is correct?

Accepted Answer

Both A and B are correct. The crankcase depression regulator prevents overpressurizing an engine's crankcase and prevents dirt from entering the engine through seals and gaskets.

Question 14

Which of the following reasons best explains why air induction system noise is louder on a diesel engine than on a gasoline-fueled engine?

Accepted Answer

Increased amount of valve overlap.

Question 15

Which of the following instruments is the best to use to measure air inlet restrictions?

Accepted Answer

The answer of Which of the following instruments is the...

Question 16

Which of the following methods can best detect a leaking air intake system?

Accepted Answer

The answer of Which of the following methods can best...

Question 17

Which of the following practices is recommended for servicing a restricted air filter?

Accepted Answer

Replacing the filter is recommended because cleaning methods can damage the filter or fail to restore its full efficiency.

Question 18

While two technicians are examining a piston crown that has vertical cracks through the edges of the piston's combustion chamber bowl, Technician A suggests the piston crown was not getting properly cooled due to low mass airflow in the combustion chamber during the valve overlap period. Technician B suggests the cracks were caused by inadequate cooling by the oil cooler nozzles. Who is correct?

Accepted Answer

Technician A is correct because the vertical cracks through the edges of the piston's combustion chamber bowl are most likely caused by insufficient cooling of the piston crown due to low mass airflow in the combustion chamber during the valve overlap period.

Question 19

What happens to the mass of intake airflow into an engine when the EGR is enabled?

Accepted Answer

When EGR (Exhaust Gas Recirculation) is enabled, some of the exhaust gases are recirculated back into the intake, reducing the amount of fresh air entering the engine, thus decreasing the mass of intake airflow.

Question 20

What effect will high inlet air temperature combined with high humidity have on engine performance?

Accepted Answer

High inlet air temperature combined with high humidity reduces air density, leading to less oxygen available for combustion, which results in lower power output.

Quiz 14: Air Induction and Crankcase Ventilation Systems