Gasoline Fuel Systems
Chapter 48
- 1.
The most important job of the fuel system is to optimize engine performance while:
- A.
Keeping fuel consumption and emissions to a minimum.
- B.
Keeping car owners happy with acceptable vehicle performance.
- C.
Making sure all DMV rules are adhered to.
- D.
Making sure all DMV rules are adhered to.
Correct Answer
A. Keeping fuel consumption and emissions to a minimum.Explanation
Fuel consumption and emissions regulation are the two most important factors in today's automotive engineering.Rate this question:
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- 2.
Early mechanically operated fuel systems typically sprayed:
- A.
Fuel from an injector in the throttle body on the intake manifold.
- B.
A pulsed stream of fuel delivered behind the intake valves.
- C.
A sequential delivery of fuel from individual injectors on the intake manifold.
- D.
A continuous flow of fuel through injectors at each intake port.
Correct Answer
D. A continuous flow of fuel through injectors at each intake port.Explanation
The first fuel injectors were not as sophisticated as today's designs. Later technology allows us to time when the injectors open, and for what length of time.Rate this question:
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- 3.
All of these are advantages of electronically controlled fuel injection over mechanical injection systems EXCEPT:
- A.
Continuous air–fuel adjustments are possible.
- B.
Reduced emissions are achieved.
- C.
Fuel can be delivered in a continuous stream.
- D.
Reduced fuel consumption is achieved.
Correct Answer
C. Fuel can be delivered in a continuous stream.Explanation
Continuous tweeking of air-fuel ratios, reducing emissions, and reducing fuel consumption are products of advancements in automotive engineering.Rate this question:
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- 4.
Tech A says that an electronic control unit (ECU)/power train control module (PCM) is needed to make electronic fuel injection (EFI) function correctly. Tech B says that most early EFI systems were throttle body injection (TBI) type systems. Who is correct?
- A.
Tech A
- B.
Tech B
- C.
Both Techs A and B
- D.
Neither Tech A nor B
Correct Answer
C. Both Techs A and BExplanation
A computer is required to control the timing of injectors and how long they will be open.
The earliest forms of fuel injection were through one injector into the throttle body.Rate this question:
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- 5.
All of these are subsystems of modern fuel injection systems EXCEPT:
- A.
A fuel supply system.
- B.
An emissions system.
- C.
An air supply system.
- D.
A fuel metering system.
Correct Answer
B. An emissions system.Explanation
Emissions is a product of the other 3 systems. It is not controlled by a control module / computer.Rate this question:
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- 6.
Which of these fuel characteristics helps to prevent the air–fuel mixture from spontaneously igniting in the combustion chamber?
- A.
The ignition temperature
- B.
The octane rating
- C.
The cetane rating
- D.
The antiknock rating
Correct Answer
B. The octane ratingExplanation
Octane is the volatility rating of fuel.Rate this question:
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- 7.
For gasoline to burn properly, it must be mixed with the right amount of:
- A.
Carbon.
- B.
Air.
- C.
Hydrogen.
- D.
Lead.
Correct Answer
B. Air.Explanation
Remember chemistry. What are required for the reaction of combustion?Rate this question:
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- 8.
Which of these describes when the air–fuel mixture spontaneously ignites before the spark plug fires?
- A.
Detonation
- B.
Advanced ignition
- C.
Spark advance
- D.
Pre-ignition
Correct Answer
D. Pre-ignitionExplanation
What prefix is needed to define something that occurs before the desired time?Rate this question:
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- 9.
Tech A says that a slightly lean mixture offers good fuel economy and low exhaust emissions. Tech B says that a mixture that is too rich fouls spark plugs and causes incomplete burning. Who is correct?
- A.
Tech A
- B.
Tech B
- C.
Both Techs A and B
- D.
Neither Tech A nor B
Correct Answer
C. Both Techs A and BExplanation
Both Tech A and Tech B are correct. A slightly lean mixture, meaning there is more air than fuel, can indeed offer good fuel economy and low exhaust emissions. On the other hand, a mixture that is too rich, meaning there is more fuel than air, can foul spark plugs and cause incomplete burning. Therefore, both statements are accurate.Rate this question:
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- 10.
For a gasoline engine, the optimum air to fuel ratio by mass is about:
- A.
12.1:1.
- B.
14.7:1.
- C.
16.3:1.
- D.
18.5:1.
Correct Answer
B. 14.7:1.Explanation
14.7:1 is the ratio needed for ideal combustion.Rate this question:
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- 11.
The term “stoichiometric ratio” describes the chemically correct air–fuel ratio necessary to achieve all of these EXCEPT:
- A.
Complete combustion of the fuel and air.
- B.
Good fuel economy.
- C.
Maximum engine power.
- D.
Reasonably clean emissions.
Correct Answer
C. Maximum engine power.Explanation
The other three are disregarded when all we want is the upper level of engine power. The stoichiometric ratio will result in a higher level of the others listed.Rate this question:
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- 12.
Tech A says that most fuel-injected vehicles use one or two electrical pumps to supply the fuel system with pressurized fuel. Tech B says that with today's systems, a fuel pump is likely to be located inside the fuel tank. Who is correct?
- A.
Tech A
- B.
Tech B
- C.
Both Techs A and B
- D.
Neither Tech A nor B
Correct Answer
C. Both Techs A and BExplanation
Electrical pumps are the standard when it comes to cars with electronic fuel injection. These pumps are in the tank, submersed in fuel for most of their existence.Rate this question:
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- 13.
A resistor that changes its resistance with changes of temperature is called a:
- A.
Thermistor.
- B.
Transistor.
- C.
Potentiometer.
- D.
Rheostat.
Correct Answer
A. Thermistor.Explanation
What is used to check your body temperature? Now think of that electrically.Rate this question:
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- 14.
Modern fuel filters typically have all of these characteristics EXCEPT:
- A.
They use pleated paper as a filter element.
- B.
They prevent small amounts of water from getting past.
- C.
They serve as an accumulator to quiet the system.
- D.
They are directional in nature.
Correct Answer
C. They serve as an accumulator to quiet the system.Explanation
They do not quite the system. Pumps most often have a whine, but the filter does nothing to lessen it.Rate this question:
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- 15.
Which of these is a sensor for measuring crankshaft position?
- A.
Camshaft position sensor (CMP)
- B.
Crankshaft position sensor (CKP)
- C.
Intake air temperature (IAT)
- D.
Manifold absolute pressure sensor (MAP)
Correct Answer
B. Crankshaft position sensor (CKP)Explanation
The CKP is responsible for monitoring the position of the crankshaft with respect to degrees of rotation.Rate this question:
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- 16.
The purpose of the vehicle speed sensor (VSS) is to measure the:
- A.
Turbulence in the incoming airstream.
- B.
Throttle position.
- C.
Speed of the vehicle.
- D.
Coolant temperature.
Correct Answer
C. Speed of the vehicle.Explanation
VSS is an acronym for vehicle speed sensor.Rate this question:
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- 17.
The barometric pressure (BARO) sensor works in conjunction with the:
- A.
Mass airflow (MAF) sensor.
- B.
Manifold absolute pressure (MAP) sensor.
- C.
Vehicle speed sensor (VSS).
- D.
Intake air temperature (IAT) sensor.
Correct Answer
B. Manifold absolute pressure (MAP) sensor.Explanation
The barometric pressure sensor is an input that tells the engine control computer the ambient pressure of atmospheric air. The MAP does the same, but reports the engine intake manifold pressure.Rate this question:
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- 18.
Which of these has the function of monitoring the noise that is created by a pressure spike in the combustion chamber?
- A.
Barometric pressure (BARO) sensor
- B.
Manifold absolute pressure (MAP) sensor
- C.
Detonation sensor
- D.
Knock sensor
Correct Answer
D. Knock sensorExplanation
When there is pre-ignition or detonation, there is a physical disturbance in the engine block/ The knock sensor is an input that tells the engine control computer that there is an undesirable explosion in the combustion chamber.Rate this question:
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- 19.
Tech A says that engine misfiring will cause a lean exhaust condition. Tech B says that engine misfiring can cause overheating of the catalytic converter. Who is correct?
- A.
Tech A
- B.
Tech B
- C.
Both Techs A and B
- D.
Neither Tech A nor B
Correct Answer
B. Tech BExplanation
When an cylinder misfires, the fuel remains unburned. The catalyst speeds the reaction of converting unwanted combustion by-products into safer emissions. This process is exothermic and is exaggerated when there is an excess of hydrocarbons in the exhaust.Rate this question:
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- 20.
The on and off time of a stepper motor relates to its duty cycle, which is generally expressed as a:
- A.
Percentage.
- B.
Numeric value.
- C.
Binary number.
- D.
Hexi-decimal value.
Correct Answer
A. Percentage.Explanation
The amount of time something is on or off, the duty cycle, is expressed as a percentage.Rate this question:
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- 21.
A variation in pulse width at a fixed frequency is called:
- A.
Duty cycle.
- B.
Analog cycle.
- C.
Pulse-width modulation.
- D.
Digital cycle.
Correct Answer
C. Pulse-width modulation.Explanation
The control for the duty cycle is called a pulse width modulation.Rate this question:
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- 22.
Tech A says that fuel pump pressure can often be tested by accessing a test port. Tech B says that fuel pump volume can be affected by the condition of the fuel injectors. Who is correct?
- A.
Tech A
- B.
Tech B
- C.
Both Techs A and B
- D.
Neither Tech A nor B
Correct Answer
A. Tech AExplanation
If there is a test port to test supply pressure, that's the way to go.
The fuel pump determines the amount of fuel delivered. The injectors only open and close.Rate this question:
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- 23.
A fuel pump can be tested using a lab scope and a low-amp clamp to:
- A.
Graph the current flow.
- B.
Measure the fuel pressure.
- C.
Measure the volume.
- D.
Test for pressure loss due to leaks.
Correct Answer
A. GrapH the current flow.Explanation
Monitoring current draw of a fuel pump is very helpful in diagnosing no start conditions.Rate this question:
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- 24.
The engine misfire monitor directly detects a fault by monitoring:
- A.
Exhaust emissions.
- B.
Crankshaft rpm.
- C.
Cylinder head temperature.
- D.
Transmission output shaft rpm.
Correct Answer
B. Crankshaft rpm.Explanation
If a cylinder isn't firing, the crankshaft speed will slow down for the effected cylinder.Rate this question:
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- 25.
The power train control module (PCM) must control a high-current fuel pump. The best actuator to use would be a:
- A.
Bipolar transistor.
- B.
MOSFET.
- C.
Relay.
- D.
Set of drivers.
Correct Answer
C. Relay.Explanation
Relays act as a bridge between a circuit requiring a high current and a circuit needing low current. Keep in mind, high and low are relative terms.Rate this question:
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Mar 21, 2023Quiz Edited by
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