Engine Systems Flashcards
The capacity of a cooling system is 9.5 litres. Which antifreeze mixture will provide adequate protection for winter, at the lowest cost?
a. 2.5L of coolant and 7L of distilled water
b. 3.5L of distilled water and 6.0L of coolant
c. 5.0L of coolant and 4.5L of distilled water
d. 6.5L of coolant and 3.0L of distilled water
c. 5.0L of coolant and 4.5L of distilled water
Testing an engine coolant temperature sensor shows 100 000 ohms resistance at -40 Celsius and 70 ohms at 130 Celsius. What does this indicate?
a. The sensor is functioning normally within its design limits.
b. The sensor circuit is shorted in the power-train control module.
c. The sensor is shorted when hot, bypassing all controls.
d. The engine coolant temperature sensor has ground fault.
a. The sensor is functioning normally within its design limits.
A customer reports that coolant is being lost. Coolant was recently added to a hot engine. The customer now notices white smoke from the exhaust when the engine is loaded. During a cooling system pressure test, the pressure drops slowly but no external leaks are seen. What is the problem?
a. The intake manifold is leaking into the crankcase.
b. The cylinder head gasket is leaking, pressurizing the cooling system.
c. The transmission cooler is leaking coolant into the transmission.
d. The cylinder head has cracked and is leaking coolant into the combustion chamber.
d. The cylinder head has cracked and is leaking coolant into the combustion chamber.
An oil pressure test reveals low oil pressure at idle and lower than expected oil pressure at 2500 rpm. What do these results indicate?
a. The oil pump pressure relief valve is stuck closed.
b. There is a leak in the oil filter.
c. There is significant wear in the engine bearings.
d. The oil return passages are plugged and the engine is starved of oil.
c. There is significant wear in the engine bearings.
What is indicated by the results below from engine compression and cylinder leakage tests?
Compression Cylinder Leakage
Cyl 1 145 psi 49%
Cyl 2 157 psi 51%
Cyl 3 167 psi 68%
Cyl 4 150 psi 60%
a. The rings are worn in all cylinders.
b. Valve seals and valve guides are leaking.
c. The timing chain is loose and has jumped.
d. Valve sealing is poor in all cylinders.
a. The rings are worn in all cylinders.
An engine is described as being "sluggish". The vacuum reading at idle is 17" Hg. On a snap throttle test, the vacuum drops to 8" Hg then rebounds to 18" Hg. The vacuum reading drops off slowly when the engine is held at 2500 rpm. What do these results indicate? a. A stretched timing chain b. A burned exhaust valve c. A restricted exhaust system A rich fuel/air mixture
c. A restricted exhaust system
A tech has identified a cooling system leak in the radiator. The leak is isolated in the radiator core. What repairs should be done?
a. The radiator should be flushed and then refilled with good quality coolant.
b. The radiator should be cleaned and then repaired by crimping the leaking tube.
c. The radiator core should be repaired or replaced and then refilled with good quality coolant.
d. The affected tubes of the core should be isolated and then abandoned.
c. The radiator core should be repaired or replaced and then refilled with good quality coolant.
While pressure testing a cooling system, a tech notices a leak from the water pump. What should be done?
a. Drain the system, remove the pump drive belt and the timing belt if required, replace the water pump, then refill and bleed the system.
b. Drain the system, fill the hole with silicone, refill and retest for further leakage.
c. Check the oil for coolant contamination. If present, replace the engine.
d. Flush the cooling system, replace the water pump, add coolant conditioner and leak stopping material to the system.
a. Drain the system, remove the pump drive belt and the timing belt if required, replace the water pump, then refill and bleed the system.
What is the procedure to check the coolant serviceability?
a. The coolant should be drained, then the correct volume of a 50% solution installed.
b. Coolant should be checked for pH level using a voltmeter, for electrolytic level using an ohmmeter, and for concentration using a hydrometer.
c. A coolant additive package should be added to restore the coolant quality before testing.
d. Coolant should be checked for pH level using a test strip, for electrolytic level using a voltmeter, and for concentration using a refractometer.
d. Coolant should be checked for pH level using a test strip, for electrolytic level using a voltmeter, and for concentration using a refractometer.
A tech finds that the clearances in the oil pump are excessive. What repairs should be done?
a. The rotors or gears should be replaced and the bore resized.
b. Install a larger relief spring and an oil filter bypass valve.
c. The complete pump assembly should be discarded and replaced.
d. A larger gear set should be installed and the system pressure checked.
c. The complete pump assembly should be discarded and replaced.
What is the correct procedure to install a 0.020” oversize piston?
a. Bore the cylinder to 0.020” oversize, then hone to provide a suitable finish.
b. Subtract the clearance required, bore the cylinder to that size, then hone for clearance.
c. Measure the piston, bore the cylinder to actual piston size, then hone for clearance.
d. Bore the cylinder to 0.022” to provide clearance, then hone to a suitable finish.
c. Measure the piston, bore the cylinder to actual piston size, then hone for clearance.
When installing new bearings, what should be done to verify bearing clearance during final assembly?
a. Look for cast codes on the counterweights of the crankshaft and install bearing shells to match.
b. Look on the back of the original bearing shells for size information and install new shells of the same size.
c. Measure the bore diameter to determine oversize required and the journal diameter to determine the undersize required.
d. Install replacement bearings and use “Plastigage” to measure the installed clearance.
d. Install replacement bearings and use “Plastigage” to measure the installed clearance.
A multiport V6 engine is running rough and appears to be starved for fuel on two of three cylinders on a bank-fire injection system. Adding propane seems to improve the idle and drivability. A cylinder balance test indicates low power contribution from cylinders 1 and 5. Further testing proves there are no vacuum leaks. What causes this condition?
a. The powertrain control module has a failing injector driver.
b. Restricted injectors on cylinders 1 and 3
c. An open in the injector winding of cylinder 3
d. An injector with low resistance in cylinder 3
d. An injector with low resistance in cylinder 3
A vehicle with port injection is hard to start after sitting for an hour or more. A fuel pressure test shows that the fuel pressure is normal, but quickly drops to zero after the engine is turned off. What causes this condition?
a. A defective fuel pump
b. A plugged fuel injector
c. A defective fuel pump check valve
d. Fuel pressure regulator stuck closed
c. A defective fuel pump check valve
A vehicle equipped with a distributor ignition system is hard starting when cold. Which of the following conditions would cause this?
a. Spark plugs gapped too closely
b. Poorly grounded ignition module
c. Wires installed on distributor cap incorrectly
d. An open coil wire to the distributor cap
a. Spark plugs gapped too closely
The engine idles poorly but runs fine at 2000 rpm. What is the cause?
Scan Tool Idle 2000 rpm
TPS 0.7 volts 1.5 volts
CTS 76 deg 76 deg
MAP 83 kPa 31 kPa
HO2S Varying from 725-900mV Varying from 225-900mV
RPM 550 2050
IAC 50 20
a. The engine is running rich.
b. The EGR valve is not seating.
c. One or more injectors are clogged.
d. The engine is overheating.
b. The EGR valve is not seating.
A tech performing an emission test finds high CO and HC. Which test would confirm a suspected defective catalytic converter?
a. Outlet temperature would be notably higher than inlet temperature.
b. Exhaust gas back-pressure should not exist ahead of the catalytic converter.
c. Engine vacuum should stay up during a cruise check and respond quickly during a snap throttle test.
d. When the converter should not rattle when struck with a hammer.
a. Outlet temperature would be notably higher than inlet temperature.
After road testing for lack of power, a tech notices a hot smell from under the car and a catalytic converter that has an orange glow. What causes this condition?
a. A disconnected spark plug wire
b. A broken air pump drive belt
c. A plugged canister purge vacuum hose
d. A plugged fuel injector
a. A disconnected spark plug wire
A vehicle failed enhanced emissions for high oxides of nitrogen. What is causing this problem?
Scan Tool Idle
TPS 0.55 volts
CTS 80 degrees
MAP 40 kPa
HO2S Varying from 100mV-900mV
a. The engine is running too hot.
b. The MAP sensor vacuum is below 9” Hg.
c. The EGR solenoid has an open ground.
d. Fuel vapours are being drawn into the intake.
c. The EGR solenoid has an open ground.
During an enhanced I/M test, a vehicle passed the pressure test but failed the evaporative purge flow test. No DTC’s were recorded. While running the vehicle with the throttle held open, the scan tool display indicates that the EVAP solenoid is commanded on. What caused the failed test?
a. EVAP solenoid shorted
b. EVAP solenoid open
c. Blocked vacuum port to solenoid
d. Vacuum leak at valve diaphragm
c. Blocked vacuum port to solenoid
A vehicle failed an enhanced emission test for high HC. The readings were obtained during an exhaust analysis, with the Air Injection Reaction system disabled. What is causing the problem?
Scan Tool Idle 2000 rpm
HC 660 ppm 69 ppm
CO 0.0 % 0.22 %
CO2 10.9 % 13.9 %
O2 2.1 % 0.1 %
a. Defective catalytic converter
b. A grounded ignition wire
c. A leaking power brake booster
d. Base timing is retarded 3 degrees
c. A leaking power brake booster
When installing a fuel pressure tester on a multiport fuel injection system, what procedure must be followed to obtain accurate pressure readings?
a. Relieve the rail pressure, then install and bleed the gauge.
b. Install the gauge, then relieve the pressure in the line.
c. Disconnect the fuel line, then install the gauge.
d. Remove the power fuse, then bleed out air in the the line.
a. Relieve the rail pressure, then install and bleed the gauge.
A fuel pump is suspected of being faulty. What is a quick check to confirm the fuel pump relay is working?
a. Test for power at the pump and then cycle the ignition key off.
b. Back probe the relay terminal with a test light, then cycle the key on.
c. Install a scan tool, and then check the data stream.
d. Remove the fuel pump relay, then feel for a click.
b. Back probe the relay terminal with a test light, then cycle the key on.
What is the procedure for diagnosing a no-start condition in a multiport fuel injected vehicle?
a. First determine there is no injector pulse or spark, then test for an open circuit at the crankshaft position sensor.
b. First test the battery voltage level, then inspect the spark wires with a high impedance digital ohmmeter.
c. First confirm the complaint, then test the fuel system pressure and compare to specs.
d. First install the scan tool, then perform a bidirectional test to fire the spark plugs.
a. First determine there is no injector pulse or spark, then test for an open circuit at the crankshaft position sensor.
What is indicated by the cylinder hear bolt torque specifications shown?
Initial pass 30Nm
2nd pass 65 degrees
a. Head bolts must be torqued to 30Nm, them warm the engine to 65 degrees before retorquing to 30Nm.
b. All head bolts must first be torqued to 30Nm, then all turned another 65 degrees.
c. Each head bolt must be torqued to 30Nm, then immediately turned another 65 degrees.
d. Head bolts must be torqued to 30Nm, bring the engine to full operating temperature, then turn the bolts another 65 degrees.
b. All head bolts must first be torqued to 30Nm, then all turned another 65 degrees.
Which procedure describes the process for replacing an exhaust gas recirculation valve?
a. Ensure the valve is cool then torque the bolts to specs.
b. Ensure the passage is open, then operate the valve.
c. Ensure the valve is the correct type, then clear the passage in the intake.
d. Ensure the passage is blocked, then replace with the correct valve.
c. Ensure the valve is the correct type, then clear the passage in the intake.
When testing fuel control system response by creating a vacuum leak, what two things should be observed?
a. A voltage drop in O2 sensor output and an increase in injector dwell.
b. A voltage rise in O2 sensor output and a decrease in injector dwell.
c. A decrease in RPM and an advance in spark timing.
d. An increase in RPM and a drop in spark advance.
a. A voltage drop in O2 sensor output and an increase in injector dwell.
A cylinder compression test will detect all of the following problems EXCEPT:
a. Valve not seating
b. Worn valve guides
c. Broken piston ring
d. Leaking head gasket
b. Worn valve guides
The first step in diagnosing a performance or drivability issue is to:
a. Perform a preliminary inspection
b. Verify the problem with a road test
c. Look for specific information from the customer
d. Eliminate the possibility of an internal engine problem
c. Look for specific information from the customer
When using a timing light to isolate an engine noise, expect top end noises to occur:
a. With every other flash of the timing light
b. With every flash of the timing light
c. Twice for every flash of the timing light
d. Between each flash of the timing light
b. With every flash of the timing light?
When performing an manifold vacuum test, raising the engine speed off idle will cause gauge readings to:
a. Increase slightly
b. Decrease slightly
c. Fluctuate rapidly
d. Remain constant
a. Increase slightly
During a compression test, a cylinder reads low on the first stroke, builds up slightly, and then level off below specification. The most likely cause would be:
a. Sticking or burned valves
b. Worn piston rings or damaged piston
c. Leaking head gasket or cracked head
d. Worn cylinder walls and excessive blow by
a. Sticking or burned valves
What would be the seating ability of a cylinder with a 28 percent loss of air pressure during a leakage test?
a. Good
b. Fair
c. Poor
d. Bad
c. Poor
Which test can be performed on a running engine to quickly detect internal problems?
a. Cylinder compression
b. Cylinder leakage
c. Cylinder power balance
d. Oscilloscope
c. Cylinder power balance
A vacuum gauge connected to an engine reads 18hg at idle. When the engine speed is increased, the gauge momentarily drops to near zero, then slowly rises and stabilizes at 9hg. The likely cause of these readings would be:
a. Weak piston rings
b. Incorrect fuel mixture
c. Restricted exhaust
d. Retarded ignition timing
c. Restricted exhaust
A cylinder compression test reveals fairly even compression but lower than specs. A second wet test results in higher readings on all cylinders. These results indicate:
a. Poor valve seating
b. Worn valve guides
c. Worn piston rings
d. Leaking head gasket
c. Worn piston rings
The needle of a vacuum gauge rapidly vibrates between 14 and 18”Hg with the engine running at idle. As the engine speed increases, the gauge stops vibrating and stabilizes. These readings are most likely caused by:
a. Weak piston rings
b. Incorrect fuel mixture
c. Worn valve guides
d. Weak valve springs
b. Incorrect fuel mixture
Which of the following is the proper procedure for performing a cylinder balance test?
a. Run the engine at idle, short the spark plug on at a time, and note any rpm drop.
b. Run the engine at 1500 rpm, short the spark plugs two and a time, and not any rpm drop.
c. Run the engine at idle, short all but two spark plugs, and not any rpm drop.
d. Run the engine at 1500 rpm, short the spark plugs one at a time, and note any rpm drop.
d. Run the engine at 1500 rpm, short the spark plugs one at a time, and note any rpm drop?
The needle on a vacuum gauge oscillates back and forth when the engine is at idle. this generally indicates which of the following? a. Late valve timing b. Poor air fuel mixture c. A blown cylinder head gasket d An air leak in the intake manifold
b. Poor air fuel mixture
After facing, the valves must have a margin of at least:
a. 1/64”
b. 1/32”
c. 1/16”
d. 1/8”
b. 1/32”
Resurfacing an OHC cylinder head will:
a. Increase valve timing
b. Alter cam timing
c. Change valve lash
d. Lower compression
b. Alter cam timing
Valve spring installed height is measured from:
a. Spring seat to valve tip
b. Valve guide top to valve keeper groove
c. Valve retainer top to valve stem end
d. Spring seat to valve retainer
d. Spring seat to valve retainer
Which of the following method is NOT used for detecting cracks in a cast iron cylinder head?
a. Dye penetrate test
b. Pressure test
c. Magnetic particle testing
d. Leak down testing
a. Dye penetrate test
A cylinder bore measurement indicates 3.067” below ring travel at the bottom and 3.077” below ridge at the top. The standard factory bore is 3.065”. What would be the proper repair?
a. Deglaze the cylinder walls and install the old piston with new cast iron rings.
b. Bore and hone the cylinder 3.097” and install 0.030” over size pistons with new rings.
c. Bore and hone the cylinder to 3.075” and install knurled pistons with new rings.
d. Bore and hone the cylinder to 3.095” and install 0.030” over size pistons with new rings
d. Bore and hone the cylinder to 3.095” and install 0.030” over size pistons with new rings.
Two cylinder bore measurements are taken: one perpendicular (at right angle) to the crankshaft and the other in line with the crankshaft. These two measurements are used to determine:
a. Cylinder out of round
b. Cylinder taper
c. Cylinder warpage
d. Cylinder ridge
a. Cylinder out of round
In a high mileage engine, cylinder wear is normally the greatest at the:
a. Top of the cylinder measured parallel to the crankshaft
b. Top of the cylinder measured at right angle to the crankshaft
c. Bottom of the cylinder measured parallel to the crankshaft
d. Bottom of the cylinder measured at right angle to the crankshaft
b. Top of the cylinder measured at right angle to the crankshaft
A diagonal or angled wear pattern on the thrust surface of a piston is an indication of:
a. A bent connecting rod
b. Too much piston pin clearance
c. An out of round cylinder bore
d. A collapsed piston skirt
a. A bent connecting rod
For engine rebuilding, the use of a dial indicator is for:
a. Ring end gap
b. Piston to cylinder end gap
c. End play in a camshaft
d. Valve seat angle
c. End play in a camshaft
