Question 1

-If an engine is leaking coolant into its cylinders, which of the following would most likely result?
A) black smoke emission
B) green smoke emission
C) red smoke emission
D) white smoke emission

Accepted Answer

When coolant leaks into the engine cylinders, it can cause white smoke to be emitted from the exhaust due to the coolant burning off.

Question 2

Blue smoke emission from a truck diesel engine is usually caused by:
A) an oil leak
B) semi-combusted oil in the exhaust gas
C) over-fueling
D) air starvation

Accepted Answer

Blue smoke from a diesel engine typically indicates that oil is being burned in the combustion chamber, which is often due to semi-combusted oil in the exhaust gas.

Question 3

If an engine is tested and found to be emitting high NOx, what color would the exhaust gas emission be?
A) blue
B) white
C) black
D) clear

Accepted Answer

High NOx emissions do not typically change the color of the exhaust gas, so it would likely remain clear.

Question 4

A diesel engine is emitting black smoke, especially under load. Which of the following should be performed first?
A) check inlet restriction on fuel suction side
B) check air filter inlet restriction
C) check for high exhaust back pressure
D) perform an engine overhead adjustment

Accepted Answer

Black smoke from a diesel engine, especially under load, typically indicates incomplete combustion due to insufficient air. Checking the air filter inlet restriction (B) should be the first step, as a clogged air filter can significantly reduce the amount of air available for combustion, leading to the production of black smoke.

Question 5

How should a cylinder misfire be checked out on an electronically-controlled fueled diesel engine?
A) sequentially short out each injector by cracking each high pressure pipe
B) remove the exhaust manifold and check for smoke
C) mechanically hold the EUI rocker in its down position
D) use an EST to perform an electronic cylinder cutout test

Accepted Answer

An electronic cylinder cutout test, performed using an Electronic Service Tool (EST), is the correct method for checking a cylinder misfire on an electronically-controlled fueled diesel engine. This method allows for precise diagnostics without physically altering or damaging the engine components.

Question 6

What color smoke is associated with diesel engine start-up in extreme cold weather conditions?
A) gray
B) black
C) blue
D) white

Accepted Answer

White smoke is associated with diesel engine start-up in extreme cold weather conditions, indicating incomplete combustion due to the cold engine not being able to adequately heat the fuel to a point where it can combust completely.

Question 7

When troubleshooting the cause of low oil pressure readings on a dash gauge, which of the following should be done first?
A) rebuild the oil pump
B) replace the piston oil control rings
C) check with a master gauge
D) reset the pressure relief valve

Accepted Answer

Checking with a master gauge should be done first to verify the accuracy of the dash gauge reading before proceeding with more invasive repairs.

Question 8

What is the most likely result of a diesel engine with too much oil in the sump?
A) blue smoke emission
B) aerated engine oil
C) engine runaway
D) hard cranking

Accepted Answer

Too much oil in the sump can lead to aerated engine oil because the crankshaft can whip the excess oil into a froth, introducing air into the oil and reducing its lubricating properties.

Question 9

Which of the following instruments is designed for testing the exhaust gas temperature in a diesel engine?
A) digital multimeter (DMM)
B) scan tool
C) pyrometer
D) thermistor

Accepted Answer

A pyrometer is specifically designed to measure the temperature of exhaust gases in engines, including diesel engines.

Question 10

If the aneroid device on a hydromechanical diesel engine has been tampered with, which of the following is more likely?
A) increase in black smoke emission
B) increase in white smoke emission
C) reduction in engine power
D) increased engine power

Accepted Answer

The aneroid device controls the fuel delivery based on air pressure. Tampering with it can lead to excessive fuel delivery, causing incomplete combustion and increased black smoke emission.

Question 11

Which of the following can restrict a secondary fuel filter sufficiently to shut down diesel engine?
A) diesel fuel conditioner
B) Water
C) alcohol
D) kerosene

Accepted Answer

Water in the fuel can lead to the restriction of a secondary fuel filter, as it does not compress or flow like diesel fuel, potentially causing blockages that can shut down a diesel engine.

Question 12

Which of the following is the more likely cause of an engine hunting condition?
A) unbalanced fuel delivery by injectors
B) damaged aneroid device
C) low CN value of fuel
D) plugged air filter

Accepted Answer

Unbalanced fuel delivery by injectors can cause inconsistent engine performance, leading to hunting as the engine struggles to maintain a steady speed.

Question 13

Which of the following can cause abnormally high DPF intake temperatures?
A) restricted boost air heat exchanger
B) high air filter inlet restriction
C) high altitude operation
D) any of the above

Accepted Answer

Each of the listed factors can contribute to abnormally high Diesel Particulate Filter (DPF) intake temperatures by affecting the engine's air intake and combustion efficiency.

Question 14

What is a common cause of injector scuffing?
A) use of 1D diesel fuel
B) adding methyl hydrate to fuel tank
C) prolonged periods of high engine loading
D) running at excessive road speeds

Accepted Answer

The answer of What is a common cause of injector...

Question 15

Which of the following conditions could result in high engine exhaust temperature?
A) Advanced injection timing
B) Leak in the air intake circuit
C) Restricted air intake system
D) All of the above

Accepted Answer

All of the listed conditions can lead to high engine exhaust temperatures. Advanced injection timing can cause the fuel to burn at a higher temperature. A leak in the air intake circuit or a restricted air intake system can reduce the amount of air available for combustion, leading to incomplete combustion and higher exhaust temperatures.

Question 16

All of the following can cause a low oil pressure condition EXCEPT:
A) fuel in lube
B) excessive main bearing clearance
C) oil pump relief valve stuck closed
D) excessive rocker shaft bushing clearance

Accepted Answer

An oil pump relief valve stuck closed would actually cause high oil pressure, not low. The relief valve's purpose is to open when the oil pressure reaches a certain high threshold to prevent excessive pressure in the system. Choices A, B, and D would lead to a decrease in oil pressure due to dilution of the oil, increased space for the oil to fill, and leakage past worn components, respectively.

Question 17

Which of the following could result in abnormally high manifold boost on an engine with a VGT turbocharger?
A) sticking VGT vane ring
B) retarded injection timing
C) plugged charge air cooler
D) restricted DPF

Accepted Answer

A sticking VGT vane ring can cause the vanes to remain in a position that increases boost pressure, leading to abnormally high manifold boost.

Question 18

When inspecting a cracked DPF core, there is evidence of scorched fuel in the substrate. What should be done after replacing the DPF?
A) send a fuel sample off for testing
B) change the fuel filters
C) replace all the injectors
D) perform a cylinder balance test

Accepted Answer

The answer of When inspecting a cracked DPF core, there...

Question 19

A diesel engine produces a vibration complaint. Which of the following would be the more likely cause?
A) oil level in pan at low mark on dipstick
B) dent in the viscous vibration damper
C) broken cylinder head bolt
D) advanced injection timing

Accepted Answer

A dent in the viscous vibration damper can cause imbalance, leading to vibrations in the engine.

Question 20

Technician A says that a low oil pressure reading can be caused by insufficient oil in the crankcase. Technician B says that a low oil pressure reading can be caused by excessive oil in the crankcase. Who is correct?
A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Accepted Answer

The answer of Technician A says that a low oil...

Quiz 52: Troubleshooting and Diagnostics

-If an engine is leaking coolant into its cylinders, which of the following would most likely result?

Blue smoke emission from a truck diesel engine is usually caused by:

If an engine is tested and found to be emitting high NOx, what color would the exhaust gas emission be?

A diesel engine is emitting black smoke, especially under load. Which of the following should be performed first?

How should a cylinder misfire be checked out on an electronically-controlled fueled diesel engine?

What color smoke is associated with diesel engine start-up in extreme cold weather conditions?

When troubleshooting the cause of low oil pressure readings on a dash gauge, which of the following should be done first?

What is the most likely result of a diesel engine with too much oil in the sump?

Which of the following instruments is designed for testing the exhaust gas temperature in a diesel engine?

If the aneroid device on a hydromechanical diesel engine has been tampered with, which of the following is more likely?

Which of the following can restrict a secondary fuel filter sufficiently to shut down diesel engine?

Which of the following is the more likely cause of an engine hunting condition?

Which of the following can cause abnormally high DPF intake temperatures?

What is a common cause of injector scuffing?

Which of the following conditions could result in high engine exhaust temperature?

All of the following can cause a low oil pressure condition EXCEPT:

Which of the following could result in abnormally high manifold boost on an engine with a VGT turbocharger?

When inspecting a cracked DPF core, there is evidence of scorched fuel in the substrate. What should be done after replacing the DPF?

A diesel engine produces a vibration complaint. Which of the following would be the more likely cause?

Technician A says that a low oil pressure reading can be caused by insufficient oil in the crankcase. Technician B says that a low oil pressure reading can be caused by excessive oil in the crankcase. Who is correct?