Engine Systems Flashcards
If the vacuum valve portion of a 15 psi (103.4 kPa) radiator cap is stuck open, which of the following is most likely to happen?
A. Leakage at the radiator tanks
B. No coolant in the overflow reservoir
C. Reduced system pressure
D. Collapsed upper radiator hose when the engine is cold
Answer C
If the vacuum valve portion of the radiator cap is open, there is always an open passageway between the radiator and the overflow bottle. The vacuum valve is designed to be closed under pressure and open when the radiator pressure drops below atmospheric or coolant overflow pressure. This would lead to lower system pressure and lower the boiling point of the coolant below design.
If the main spring of a thermostat becomes weak or broken, which of the following is most likely to occur?
“A. Engine will produce more torque
B. Engine efficiency will increase.
C. Pre-ignition will occur
D. Hydrocarbon emissions will be elevated”
“Answer C
The main spring of a thermostat controls system pressure. If the spring becomes weak or fails, the system will not be able to increase pressure. remember that for every 1 psi of pressure on a contained system, it will increase the boiling point 3°CF. This result in a possible overheat condition and cause cylinder temperatures to increase. Increased cylinder temperatures will lead to pre-ignition.”
Measured oil pressure is below specifications. which of the following would be a likely cause?
“A. weak oil- pressure relief spring
B. stuck closed pressure relief valve
C. one partially clogged camshaft galley
D. Oil pump case clearance out of specification by 0,002 (0.051 mm)”
“Answer A is correct
If the oil-pressure relief spring is weak, system pressure will not build as designed. It will relieve oil pressure too early and pause system pressure to be below specifications. If the oil pump case clearance is out of specification by 0.002 (0.051 mm), it will not cause significant oil pressure problems “
If compression values increase after performing a “wet” compression test on a cylinder, which engine component should be investigated for damage or failure?
“A. Intake valve
B. Exhaust valve
C. Compression rings
D. Oil-control rings”
“Answer C
Wet compression tests are designed to take place after a dry compression test. If there is suspect cylinder or cylinders. Install about 15 ml of oil into the cylinder and preform the compression test again. If the cylinder pressure increases, investigation must go into the compression rings or cylinder wall.”
Which of the following tools is most accurate for checking coolant strength?
“A. Hydrometer
B. pH test strips
C. Refractometer
D. gas analyzer “
“Answer C
The refractometer is the most accurate for checking coolant strength. A refractometer does not measure specific gravity as a hydrometer does, but it measure concentration by the way light bends through it. This gives the most accurate measurement and is auto-temperature controlled. Also, it can handle both ethylene glycol and propylene glycol.”
If a horizontally mounted thermostat has a “jiggle valve”, at what position would the valve be placed?
“A. The bottom
B. The top
C. The side
D. Closest to the heater core”
“Answer B
The jiggle valve is designed to help bleed the cooling and prevent the formation of air pockets. The jiggle valve is normally placed in the up position or at the top of the thermostat housing. since air will tend to rise “
When installing a new gear - type oil pump, which of the following should be done?
“A. Coat the surfaces with used engine oil
B. Apply silicone to the tips of the gear teeth
C. Leave the oil pump dry; oil from the sump will lubricate.
D. Coat the pump with assembly lube.”
“Answer D is correct
Coating the pump with assembly lube will protect the pump from oil starvation and damage when first started. The lube in the passageways will also help the pump gain its prime quickly “
Plastigage would be used to measure which of the following clearances?
“A. Valve guide clearance
B. Camshaft bearing clearance
C. Oil pump side clearance
D. Swept volume”
“Answer B
Plastigage is used to accurately measure various types of bearing. In this question, camshaft bearing clearance is the only answer that plastigage would be capable of measuring accurately “
Which of the following would be the most likely cause of excessive fuel pressure?
“A. Restriction in their fuel supply line
B. Excessive current supplied to the fuel pump
C. Low engine vacuum
D. restriction in the fuel return line “
“Answer D
Pressure is a direct result of restriction. In order to have excessive fuel pressure, there must be a restriction that will not allow fuel to flow, but rather build pressure against it. A restriction in the supply line would result in low fuel pressure to the injection system; therefore, a restriction in the return line will cause excessive fuel pressure “
A vehicle has a single cylinder misfire on a group-type injection system. Which of the following is the more likely cause?
“A. Open injector PCM control circuit
B. Blown injector fuse
C. Inoperative (open) injector
D. Stuck fuel-pressure regulator”
“Answer C
If an injector is open, it will not react when electrical current is supplied to it. If it cannot react, no fuel will be injected into the particular cylinder, resulting in a single cylinder misfire, even thought the 2 or more injectors are commanded to inject together as a group”
What would be most likely cause of a loud clunking noise when accelerating in a forward gear ranges only
“A. Broken engine mount
B. Defective front universal joint
C. loose exhaust manifold
D. Broken flex plate “
“Answer A
If an engine mount is broken, it will allow the engine to move off its mount in reaction to the engine, transmission, and driveline torque. because engine mounts have mechanical links that prevents them from separating they will make a clunk noise as the two metallic pieces collide together”
Where should exhaust back pressure be tested in order to find a partially plugged catalytic convertor?
“A. At the exhaust manifold gasket
B. At the catalytic converter front gasket
C. Pre-catalytic oxygen sensor
D. Post-catalytic oxygen sensor”
“Answer C
In order to test for a partially plugged catalytic converter, testing must occur upstream or before the catalytic converter. The easiest access to the exhaust pressure is through the oxygen sensors “
Which of the following would be a likely cause of a severe piston damage
“A. retard timing
B. Detonation
C. open ignition wire
D. over rich mixture”
“Answer B
Detonation occurs when combustion happens too slowly unburned air-fuel mixture ignites, not as part of the normal ignition process and the 2 flame fronts collide. This results in a cylinder knock, and if left untreated can cause irreparable damage to the piston and/ or cylinder”
If measured piston ring side clearance is too great, which of the following might occur?
“A. Binding during installation
B. Inadequate oil drainage
C. Piston wear
D. Ring flutter”
“Answer D
Piston ring flutter is a rapid oscillation of the piston ring in the ringland. Improper side clearance can cause this problem, resulting in a loss of cylinder compression and possible breakage of the ring “
If an air injection pump has seized, which of the following is the most likely cause?
“A. Inadequate oil level
B. Belt tension too low
C. Defective check valve
D. Partially open EGR valve”
“Answer C
Air pumps are designed to inject air into the exhaust system to promote the oxidation process in the catalytic converter. Since the output of the air pump is directly connected to the exhaust system, a one-way check valve is used. This check valve, if defective, can allow hot exhaust gases into the air pump. This can lead to melting of plastic or composite components, thereby causing seizure and failure.”
During a cylinder leakage test, air is heard escaping through the oil fill. which of the following is the correct item to investigate?
“A. Piston rings
B. intake valve
C. Exhaust valve
D. Head gasket “
“Answer A
During a cylinder leakage test, if there is more than 20% leakage, this is considered poor. If the air is heard escaping from the oil fill, the air that has been injected into the combustion chamber is escaping to the crankcase. The route from the combustion chambers to the crank case is through the piston rings”
While honing a cylinder, which of the following should be used?
“A. A boring bar
B. Torque Plates
C. Detergent and water
D. a deck grinder “
“Answer B
Torque plates are plates that bolt onto the cylinder deck to mimic the stresses that the cylinder head will place on the cylinder when it is properly torqued. If machining is done without torque plates, cylinders can be machined out of round. Using the plates will allow for truer machining, less distortion, and a better overall fit”
Which of the following is the most likely cause of cylinder block cracking?
“A. Coolant with high pH level
B. Collision
C. Engine overheating condition
D. Metallurgical fatigue”
“Answer C
All of the answers in this question could lead to cylinder block cracking. With technology today, metallurgical failures do not occur as often. Collisions do occur. The most common cause of block cracking, however, is an engine overheating condition.”
Who is responsible for the vehicle emission control maintenance?
“A. Owner
B. Technician
C. Service manager
D. Manufacturer”
“Answer A
The owner is responsible for the maintenance nd safety of the vehicle because it is his or her property. Emission control maintenance is the sole responsibility of the vehicle owner “
What should you do with recovered engine coolant (ethylene glycol)?
“A. Pour it down the drain
B. Pour it in the waste oil container
C. Send it to a recycling operation
D. use it to remove oil stains in the parking lot”
“Answer C
Since ethylene glycol, or antifreeze, is toxic and harmful if ingested, it is a legal requirement that recovered engine coolant be sent to a recycling operation and there disposed of or remanufactured properly “
What should be done in the event of a significant oil spill in the garage?
“A. Wash the oil down the drain
B. apply oil absorbent, sweep it up, and dispose of it in garbage containers
C. Apply oil absorbent, sweep it up, and dispose of it with the waste oil disposal company
D. apply floor soap, scrub, and hose down the drain “
“Answer C
Oil should never be washed a drain. it should be absorbed, swept up and disposed of with an oil recycling company. This prevents any environmental infractions for pollution.”
