Gasoline Fuel Systems

1. For gasoline to burn properly, it must be mixed with the right amount of:

Carbon.

Air.

Hydrogen.

Lead.

Remember chemistry. What are required for the reaction of combustion?

Explanation

Remember chemistry. What are required for the reaction of combustion?

2. The most important job of the fuel system is to optimize engine performance while:

Keeping fuel consumption and emissions to a minimum.

Keeping car owners happy with acceptable vehicle performance.

Making sure all DMV rules are adhered to.

Fuel consumption and emissions regulation are the two most important factors in today's automotive engineering.

Explanation

Fuel consumption and emissions regulation are the two most important factors in today's automotive engineering.

3. For a gasoline engine, the optimum air to fuel ratio by mass is about:

12.1:1.

14.7:1.

16.3:1.

18.5:1.

14.7:1 is the ratio needed for ideal combustion.

Explanation

14.7:1 is the ratio needed for ideal combustion.

4. Which of these is a sensor for measuring crankshaft position?

Camshaft position sensor (CMP)

Crankshaft position sensor (CKP)

Intake air temperature (IAT)

Manifold absolute pressure sensor (MAP)

The CKP is responsible for monitoring the position of the crankshaft with respect to degrees of rotation.

Explanation

The CKP is responsible for monitoring the position of the crankshaft with respect to degrees of rotation.

5. The purpose of the vehicle speed sensor (VSS) is to measure the:

Turbulence in the incoming airstream.

Throttle position.

Speed of the vehicle.

Coolant temperature.

VSS is an acronym for vehicle speed sensor.

Explanation

VSS is an acronym for vehicle speed sensor.

6. A resistor that changes its resistance with changes of temperature is called a:

Thermistor.

Transistor.

Potentiometer.

Rheostat.

What is used to check your body temperature? Now think of that electrically.

Explanation

What is used to check your body temperature? Now think of that electrically.

7. Which of these fuel characteristics helps to prevent the air–fuel mixture from spontaneously igniting in the combustion chamber?

The ignition temperature

The octane rating

The cetane rating

The antiknock rating

Octane is the volatility rating of fuel.

Explanation

Octane is the volatility rating of fuel.

8. Which of these describes when the air–fuel mixture spontaneously ignites before the spark plug fires?

Detonation

Advanced ignition

Spark advance

Pre-ignition

What prefix is needed to define something that occurs before the desired time?

Explanation

What prefix is needed to define something that occurs before the desired time?

9. The power train control module (PCM) must control a high-current fuel pump. The best actuator to use would be a:

Bipolar transistor.

MOSFET.

Relay.

Set of drivers.

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.

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.

10. Which of these has the function of monitoring the noise that is created by a pressure spike in the combustion chamber?

Barometric pressure (BARO) sensor

Manifold absolute pressure (MAP) sensor

Detonation sensor

Knock sensor

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.

Explanation

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.

11. 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?

Tech A

Tech B

Both Techs A and B

Neither Tech A nor B

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.

Explanation

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.

12. 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?

Tech A

Tech B

Both Techs A and B

Neither Tech A nor B

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.

Explanation

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.

13. A variation in pulse width at a fixed frequency is called:

Duty cycle.

Analog cycle.

Pulse-width modulation.

Digital cycle.

The control for the duty cycle is called a pulse width modulation.

Explanation

The control for the duty cycle is called a pulse width modulation.

14. The barometric pressure (BARO) sensor works in conjunction with the:

Mass airflow (MAF) sensor.

Manifold absolute pressure (MAP) sensor.

Vehicle speed sensor (VSS).

Intake air temperature (IAT) sensor.

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.

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.

15. 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?

Tech A

Tech B

Both Techs A and B

Neither Tech A nor B

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.

Explanation

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.

16. The on and off time of a stepper motor relates to its duty cycle, which is generally expressed as a:

Percentage.

Numeric value.

Binary number.

Hexi-decimal value.

The amount of time something is on or off, the duty cycle, is expressed as a percentage.

Explanation

The amount of time something is on or off, the duty cycle, is expressed as a percentage.

17. A fuel pump can be tested using a lab scope and a low-amp clamp to:

Graph the current flow.

Measure the fuel pressure.

Measure the volume.

Test for pressure loss due to leaks.

Monitoring current draw of a fuel pump is very helpful in diagnosing no start conditions.

Explanation

Monitoring current draw of a fuel pump is very helpful in diagnosing no start conditions.

18. The engine misfire monitor directly detects a fault by monitoring:

Exhaust emissions.

Crankshaft rpm.

Cylinder head temperature.

Transmission output shaft rpm.

If a cylinder isn't firing, the crankshaft speed will slow down for the effected cylinder.

Explanation

If a cylinder isn't firing, the crankshaft speed will slow down for the effected cylinder.

19. All of these are advantages of electronically controlled fuel injection over mechanical injection systems EXCEPT:

Continuous air–fuel adjustments are possible.

Reduced emissions are achieved.

Fuel can be delivered in a continuous stream.

Reduced fuel consumption is achieved.

Continuous tweeking of air-fuel ratios, reducing emissions, and reducing fuel consumption are products of advancements in automotive engineering.

Explanation

Continuous tweeking of air-fuel ratios, reducing emissions, and reducing fuel consumption are products of advancements in automotive engineering.

20. Modern fuel filters typically have all of these characteristics EXCEPT:

They use pleated paper as a filter element.

They prevent small amounts of water from getting past.

They serve as an accumulator to quiet the system.

They are directional in nature.

They do not quite the system. Pumps most often have a whine, but the filter does nothing to lessen it.

Explanation

They do not quite the system. Pumps most often have a whine, but the filter does nothing to lessen it.

21. The term "stoichiometric ratio" describes the chemically correct air–fuel ratio necessary to achieve all of these EXCEPT:

Complete combustion of the fuel and air.

Good fuel economy.

Maximum engine power.

Reasonably clean emissions.

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.

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.

22. All of these are subsystems of modern fuel injection systems EXCEPT:

A fuel supply system.

An emissions system.

An air supply system.

A fuel metering system.

Emissions is a product of the other 3 systems. It is not controlled by a control module / computer.

Explanation

Emissions is a product of the other 3 systems. It is not controlled by a control module / computer.

23. 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?

Tech A

Tech B

Both Techs A and B

Neither Tech A nor B

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.

Explanation

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.

24. 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?

Tech A

Tech B

Both Techs A and B

Neither Tech A nor B

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.

Explanation

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.

25. Early mechanically operated fuel systems typically sprayed:

Fuel from an injector in the throttle body on the intake manifold.

A pulsed stream of fuel delivered behind the intake valves.

A sequential delivery of fuel from individual injectors on the intake manifold.

A continuous flow of fuel through injectors at each intake port.

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.

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.