ASE Diesel Engines Complete Exam Study
Questions with Verified Answers Already
Graded A+ | Brand New Version
1. When operated under load, coolant continually comes out of the radiator
overflow and there are bubbles in the radiator. The most likely cause is -
ANSWER combustion leakage into the cooling system
2. An engine with 25k miles on a major overhaul has low power, misses, low
compression, and the valves and seats are burned. The most likely cause is -
ANSWER the valves set too tight
They are not seating long enough to cool properly. Valves that remain slightly
open will have severe overheating, because the heads would be constantly
surrounded by exhaust gases.
3. A diesel engine in a new truck has blown a head gasket 3 times in the last
2000 miles. What could be the cause? - ANSWER Incorrect fuel trim
settings in the ECM
This can produce excessive cylinder pressure
4. What should be checked first on an engine with a low power complaint? -
ANSWER Fuel filter outlet pressure
5. What should be done first to find the cause of a misfire? - ANSWER Locate
the misfiring cylinder
,Then you would check the injector, compression, valve lash
6. The engine braking is weak on a compression brake. Tech A says cause
could be a stuck open solenoid valve. Tech B says the slave piston
adjustment may be loose. Who is correct? - ANSWER Tech B
A stuck open solenoid would cause engine braking to be constantly applied
7. Tech A says black smoke from a DPF equipped engine is normal. Tech B
says emission compliance is determined using opacity measurements. Who
is correct? - ANSWER Tech B
8. A cracked after cooler has been replaced on an engine and the engine now
lacks power. What is the most likely cause? - ANSWER Airflow restriction
inside the cooler
Clogging commonly exist in new after coolers.
9. The driver on a new truck says it overheats and lacks power on a long pull,
but operates normally otherwise. What is the most likely cause? - ANSWER
Too much exhaust backpressure
A slight exhaust restriction may have little effect under light load, but after
prolong time, backpressure builds up and will cause power loss
10.What could cause an engine to use too much oil? - ANSWER Worn
cylinder liners, piston rings, or turbocharger seals
11.What could cause black smoke under a heavy load? - ANSWER late
injection timing, restricted air intake, or worn injectors
, all cause engine to run rich
12.A newly rebuilt engine has failed. There are intake valve marks on all of the
pistons. This could have been caused by... - ANSWER Advanced cam
timing
This causes intake valves to open further
13.What can happen if the cylinder liner height is too low? - ANSWER
combustion leakage
14.An 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? - ANSWER Both
Restricted fuel filters cause low fuel pressure.
Restricted DPF causes exhaust restriction
15.A new wet-type cylinder liner in 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? - ANSWER Tech A
A new liner is highly unlikely to have a taper.
16.Some of the head bolt holes in the block are slightly filled with oil. Tech A
says if the bolts are torqued without cleaning the holes, the block could
crack. Tech B says if the bolts are torqued without cleaning the holes, the
bolts could be stretched. Who is correct? - ANSWER Tech A
, Oil being compressed can damage the block, not stretch the bolt.
17.A newly rebuilt engine has locked up after five minutes of operation. While
it was running, the warm-up temperature was normal. What could be the
cause? - ANSWER The main bearings were installed upside down
This will block oil holes, causing immediate failure.
18.A DPF needs to be regenerated frequently. The most likely cause is -
ANSWER extended idle and light load operation
19.An engine has low oil pressure. This could be caused by - ANSWER worn
lube oil pump
worn crankshaft main bearings - will allow oil to flow past easily
diluted oil - oil will be easier to pump
20.Turbocharger boost pressure can be measured at the - ANSWER Charge air
cooler tube
21.A restricted intake air filter can cause... - ANSWER High intake air vacuum
and reduced power
22.When checking air inlet restriction, should the engine be under load? -
ANSWER Yes
23.An engine with an overhead camshaft is having the camshaft replaced. Take
A says gear backlash can be checked with a dial indicator. Tech B says gear
Questions with Verified Answers Already
Graded A+ | Brand New Version
1. When operated under load, coolant continually comes out of the radiator
overflow and there are bubbles in the radiator. The most likely cause is -
ANSWER combustion leakage into the cooling system
2. An engine with 25k miles on a major overhaul has low power, misses, low
compression, and the valves and seats are burned. The most likely cause is -
ANSWER the valves set too tight
They are not seating long enough to cool properly. Valves that remain slightly
open will have severe overheating, because the heads would be constantly
surrounded by exhaust gases.
3. A diesel engine in a new truck has blown a head gasket 3 times in the last
2000 miles. What could be the cause? - ANSWER Incorrect fuel trim
settings in the ECM
This can produce excessive cylinder pressure
4. What should be checked first on an engine with a low power complaint? -
ANSWER Fuel filter outlet pressure
5. What should be done first to find the cause of a misfire? - ANSWER Locate
the misfiring cylinder
,Then you would check the injector, compression, valve lash
6. The engine braking is weak on a compression brake. Tech A says cause
could be a stuck open solenoid valve. Tech B says the slave piston
adjustment may be loose. Who is correct? - ANSWER Tech B
A stuck open solenoid would cause engine braking to be constantly applied
7. Tech A says black smoke from a DPF equipped engine is normal. Tech B
says emission compliance is determined using opacity measurements. Who
is correct? - ANSWER Tech B
8. A cracked after cooler has been replaced on an engine and the engine now
lacks power. What is the most likely cause? - ANSWER Airflow restriction
inside the cooler
Clogging commonly exist in new after coolers.
9. The driver on a new truck says it overheats and lacks power on a long pull,
but operates normally otherwise. What is the most likely cause? - ANSWER
Too much exhaust backpressure
A slight exhaust restriction may have little effect under light load, but after
prolong time, backpressure builds up and will cause power loss
10.What could cause an engine to use too much oil? - ANSWER Worn
cylinder liners, piston rings, or turbocharger seals
11.What could cause black smoke under a heavy load? - ANSWER late
injection timing, restricted air intake, or worn injectors
, all cause engine to run rich
12.A newly rebuilt engine has failed. There are intake valve marks on all of the
pistons. This could have been caused by... - ANSWER Advanced cam
timing
This causes intake valves to open further
13.What can happen if the cylinder liner height is too low? - ANSWER
combustion leakage
14.An 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? - ANSWER Both
Restricted fuel filters cause low fuel pressure.
Restricted DPF causes exhaust restriction
15.A new wet-type cylinder liner in 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? - ANSWER Tech A
A new liner is highly unlikely to have a taper.
16.Some of the head bolt holes in the block are slightly filled with oil. Tech A
says if the bolts are torqued without cleaning the holes, the block could
crack. Tech B says if the bolts are torqued without cleaning the holes, the
bolts could be stretched. Who is correct? - ANSWER Tech A
, Oil being compressed can damage the block, not stretch the bolt.
17.A newly rebuilt engine has locked up after five minutes of operation. While
it was running, the warm-up temperature was normal. What could be the
cause? - ANSWER The main bearings were installed upside down
This will block oil holes, causing immediate failure.
18.A DPF needs to be regenerated frequently. The most likely cause is -
ANSWER extended idle and light load operation
19.An engine has low oil pressure. This could be caused by - ANSWER worn
lube oil pump
worn crankshaft main bearings - will allow oil to flow past easily
diluted oil - oil will be easier to pump
20.Turbocharger boost pressure can be measured at the - ANSWER Charge air
cooler tube
21.A restricted intake air filter can cause... - ANSWER High intake air vacuum
and reduced power
22.When checking air inlet restriction, should the engine be under load? -
ANSWER Yes
23.An engine with an overhead camshaft is having the camshaft replaced. Take
A says gear backlash can be checked with a dial indicator. Tech B says gear
