Deck 51: Failure Analysis

Question 1

An engine is disassembled because of a single torched piston: the other five appear normal. Which of the following should be investigated first?

A) failed head gasket fire ring
B) oil cooling jet
C) water jacket scaling
D) connecting rod oil rifle

Answer 1

oil cooling jet

Question 2

When an engine is disassembled, all of the pistons show some evidence of lacquering. Which of the following is the more likely cause?

A) high temperature operation
B) low temperature operation
C) high sulfur fuel
D) failed oil control rings

Answer 2

high sulfur fuel

Question 3

When piston rings stick by gumming, what is a common cause?

A) high engine temperatures
B) coolant in combustion process
C) prolonged idling
D) prolonged lugdown

Answer 3

prolonged lugdown

Question 4

When evidence of lacquering is found on a set of crankshaft main bearings, which of the following operating and maintenance practices should be examined first?

A) quality of engine lubricating oil
B) quality of fuel
C) frequency of oil change intervals
D) frequency of bearing rollovers

Question 5

If a dry sleeve designed for a 0.0015 inch (0.038 mm) loose fit is installed to the engine block with insufficient clearance, which of the following will more likely result?

A) liner will last longer
B) liner failure due to higher cylinder pressures
C) premature liner failure due to buckling
D) cracked liners

Question 6

When a set of wet liners has evidence of severe cavitation, which of the following maintenance and operating practices should be investigated first?

A) idle shutdown duration programming
B) road speed governing
C) type of antifreeze used and service intervals
D) type of engine oil used and service intervals

Question 7

When a piston fails due to cracks in the cavity edge of the Mexican hat recess, the usual cause would be:

A) high cylinder pressures
B) overheating
C) cold weather operation
D) injector dribble

Question 8

When it is determined that a crankshaft has a torsional failure, all of the following should be balance-checked EXCEPT:

A) water pump
B) engine fan
C) vibration damper
D) flywheel

Question 9

Which of the following must be located during failure analysis investigation if a repeat is to be avoided?

A) coincidental damage
B) warranty report
C) policy adjustment
D) root cause

Question 10

When performing failure analysis on engine components, the technician is required to have an understanding of which of the following?

A) wear patterns
B) basic metallurgy
C) fractures
D) all of the above

Question 11

Technician A says that a keyway cut into a shaft is a potential stress raiser. Technician B says that oil holes in crankshafts are potential stress raisers. Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 12

Technician A says that when a component fails due to a metallurgical defect, the technician is at fault. Technician B says that a casting inclusion in a cylinder head can be classified as a metallurgical defect. Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 13

Technician A says that visual inspection is one of the most important factors of good failure analysis practice. Technician B says that laboratory analysis is usually required to accurately pinpoint root cause. Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 14

When adhesive wear occurs on crankshaft main bearing, which of the following would be the more likely cause?

A) Inappropriate lube oil
B) Prolonged high load operation
C) Prolonged low load operation
D) Irregular align bore

Question 15

Technician A says that most corrosion deterioration on engine metals is related to acids in degraded engine lube. Technician B says that most corrosion wear on engine components is either directly or indirectly related to oxidation. Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 16

When two metal components clamped by fasteners are allowed to move against each other, the result is:

A) impact damage
B) stress damage
C) fretting damage
D) fatigue damage

Question 17

Which of the following is another way of saying ductile?

A) brittle
B) flexible
C) fractured
D) abrasive

Question 18

Which type of crankshaft fracture failure would result from an excessive shock load?

A) brittle fracture
B) ductile fracture
C) fatigue fracture
D) compressional fracture

Question 19

You are inspecting a crankshaft fracture in which the fracture faces appear relatively smooth with evidence of beach marks. What type of fracture would be the likely diagnosis?

A) brittle
B) ductile
C) fatigue
D) metallurgical defect

Question 20

When a head gasket coolant leak causes a hydraulic lock in one cylinder, which of the following would be the more likely result?

A) fractured piston crown
B) fractured main bearing cap
C) connecting rod tensional failure
D) connecting rod compressional failure

Question 21

When a connecting rod separates due to a tensional overload, the root cause of the problem would most likely be:

A) excessively high cylinder pressures
B) prolonged running at high idle
C) prolonged running at low idle
D) engine overspeed

Question 22

When performing failure analysis on an EGR-aspirated diesel engine with soot build-up in the intake manifold, which of the following should you check first?

A) logged codes
B) restricted exhaust system
C) EGR control gate operation
D) EGR heat exchanger restriction

Question 23

You are determining the root cause of an older DPF that has failed because it emits continual black smoke under load but has logged no fault codes. Technician A says the seals in the turbocharger could be leaking and should be inspected. Technician B says that this can be caused by abnormally high engine temperatures so the cooling system should be checked. Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 24

Technician A says that a high percentage of EUI internal leakage problems can be related to contaminated fuel. Technician B says that internal leakage is the most common cause of EUI failures. Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 25

What type of damage can result to an EUI when fuel supply pressures fall below specification?

A) wear at the nozzle valve seat
B) wear at the pumping plunger
C) erosion at the nozzle pressure chamber
D) cavitation at the poppet control valve

Question 26

?What does Bosch research indicate is the number one reason for EHI failures?

A) ?Actuator failure
B) ?Valve seat failure
C) ?Armature set failure
D) ?Body failure

Question 27

When looking for root cause of an injector nozzle with its tip blown off which of the following should be checked first?

A) Water in the fuel system
B) Degraded diesel fuel
C) Rail pressure regulator
D) Particulate contamination in fuel

Question 28

Technician A says that the most common cause of EHI and EUI terminal post failures is overtorquing of the fasteners. Technician B says that at least one OEM permits EUI cartridge replacement in the event of a failure. Who is correct??

A) ?Technician A only
B) ?Technician B only
C) ?Both A and B
D) ?Neither A nor B