ABYC DIESEL ENGINES CERTIFICATION UPDATED
QUESTIONS AND ANSWERS
When a Diesel engine is operated under a load, coolant continually comes out of the radiator overflow
and there are bubbles in the radiator. The MOST LIKELY cause of the problem is... - CORRECT
ANSWER✅✅✅Combustion leakage into the cooling system
A Diesel engine with 25,000 miles on a major overhaul has low power and misses. It also has low
compression and the valves and seats are burned. What is the MOST LIKELY cause of these problems? -
CORRECT ANSWER✅✅✅The valves were set too tight
What can happen if the cylinder liner height is too low? - CORRECT ANSWER✅✅✅Combustion
leakage
A Diesel engine suffers from low power under load. Tech A says this could be caused by restricted fuel
filters. Tech B says this could be caused by a restricted DPF. Who is correct? - CORRECT
ANSWER✅✅✅Tech A and Tech B
A new wet-type cylinder liner is being installed in an engine block. Tech A says the liner height should be
checked. Tech B says the liner taper should be checked. Who is correct? - CORRECT
ANSWER✅✅✅Tech A
New cylinder heads are being installed on a Diesel engine and some of the head bolt holes in the block
are partially filled with oil. Tech A says that if the head bolts are torqued without cleaning the holes, the
cylinder block could crack. Tech B says that if the head bolts are torqued without cleaning, the bolts
could be stretched. Who is correct? - CORRECT ANSWER✅✅✅Tech A
A newly rebuilt engine has locked up after five minutes of operation. While it was running, the warm-up
temperature was normal. What could have been the cause of the lockup? - CORRECT
ANSWER✅✅✅The main bearings were installed upside down
A diesel engine's DPF needs to be regenerated frequently. This is MOST LIKELY caused by.... - CORRECT
ANSWER✅✅✅Extended idle and light load operation
, A Diesel engine has low oil pressure. This could be cause by... - CORRECT ANSWER✅✅✅Diluted lube
oil
What should be checked first on a Diesel engine with a low power complaint? - CORRECT
ANSWER✅✅✅Fuel filter outlet pressure
What should be done first to find the cause of a misfire on a Diesel engine? - CORRECT
ANSWER✅✅✅Find the misfiring cylinder
The engine braking is weak on a Diesel engine equipped with a compression brake. Tech A says that this
could be caused by a struck-open solenoid valve on a compression brake assembly. Tech B says that the
slave piston adjustment(s) may be loose. Who is correct? - CORRECT ANSWER✅✅✅Tech B
Tech A says that black smoke from a DPF-equipped engine is considered normal. Tech B says that diesel
emission compliance is determined using opacity measurements. Who is correct? - CORRECT
ANSWER✅✅✅Tech B
A cracked after cooler has been replaced on an engine and the engine now lacks power. What is the
MOST LIKELY cause? - CORRECT ANSWER✅✅✅There is an airflow restriction inside the cooler
The driver of a new truck says it overheats and lacks power on a long pull, but operates normally
otherwise. What is the MOST LIKELY cause? - CORRECT ANSWER✅✅✅There is too much exhaust
backpressure
Any of these could cause a Diesel engine to use too much lube oil, EXCEPT:
a. worn camshaft bushings
b. worn cylinder liners
c. worn piston rings
d. worn turbocharger seals - CORRECT ANSWER✅✅✅Worn camshaft bushings
A Diesel engine blows black smoke when under a heavy load. All of these could be the cause EXCEPT:
a. late injection timing
QUESTIONS AND ANSWERS
When a Diesel engine is operated under a load, coolant continually comes out of the radiator overflow
and there are bubbles in the radiator. The MOST LIKELY cause of the problem is... - CORRECT
ANSWER✅✅✅Combustion leakage into the cooling system
A Diesel engine with 25,000 miles on a major overhaul has low power and misses. It also has low
compression and the valves and seats are burned. What is the MOST LIKELY cause of these problems? -
CORRECT ANSWER✅✅✅The valves were set too tight
What can happen if the cylinder liner height is too low? - CORRECT ANSWER✅✅✅Combustion
leakage
A Diesel engine suffers from low power under load. Tech A says this could be caused by restricted fuel
filters. Tech B says this could be caused by a restricted DPF. Who is correct? - CORRECT
ANSWER✅✅✅Tech A and Tech B
A new wet-type cylinder liner is being installed in an engine block. Tech A says the liner height should be
checked. Tech B says the liner taper should be checked. Who is correct? - CORRECT
ANSWER✅✅✅Tech A
New cylinder heads are being installed on a Diesel engine and some of the head bolt holes in the block
are partially filled with oil. Tech A says that if the head bolts are torqued without cleaning the holes, the
cylinder block could crack. Tech B says that if the head bolts are torqued without cleaning, the bolts
could be stretched. Who is correct? - CORRECT ANSWER✅✅✅Tech A
A newly rebuilt engine has locked up after five minutes of operation. While it was running, the warm-up
temperature was normal. What could have been the cause of the lockup? - CORRECT
ANSWER✅✅✅The main bearings were installed upside down
A diesel engine's DPF needs to be regenerated frequently. This is MOST LIKELY caused by.... - CORRECT
ANSWER✅✅✅Extended idle and light load operation
, A Diesel engine has low oil pressure. This could be cause by... - CORRECT ANSWER✅✅✅Diluted lube
oil
What should be checked first on a Diesel engine with a low power complaint? - CORRECT
ANSWER✅✅✅Fuel filter outlet pressure
What should be done first to find the cause of a misfire on a Diesel engine? - CORRECT
ANSWER✅✅✅Find the misfiring cylinder
The engine braking is weak on a Diesel engine equipped with a compression brake. Tech A says that this
could be caused by a struck-open solenoid valve on a compression brake assembly. Tech B says that the
slave piston adjustment(s) may be loose. Who is correct? - CORRECT ANSWER✅✅✅Tech B
Tech A says that black smoke from a DPF-equipped engine is considered normal. Tech B says that diesel
emission compliance is determined using opacity measurements. Who is correct? - CORRECT
ANSWER✅✅✅Tech B
A cracked after cooler has been replaced on an engine and the engine now lacks power. What is the
MOST LIKELY cause? - CORRECT ANSWER✅✅✅There is an airflow restriction inside the cooler
The driver of a new truck says it overheats and lacks power on a long pull, but operates normally
otherwise. What is the MOST LIKELY cause? - CORRECT ANSWER✅✅✅There is too much exhaust
backpressure
Any of these could cause a Diesel engine to use too much lube oil, EXCEPT:
a. worn camshaft bushings
b. worn cylinder liners
c. worn piston rings
d. worn turbocharger seals - CORRECT ANSWER✅✅✅Worn camshaft bushings
A Diesel engine blows black smoke when under a heavy load. All of these could be the cause EXCEPT:
a. late injection timing
