Deck 7: Fuel System and Related Input Sensors Output Actuators Diagnosis

Question 1

Technician A says that an air leak between the MAF sensor and the throttle plate will cause the MAF sensor to indicate to the PCM that less air is entering the engine in relation to the throttle opening. Technician B says that an air leak between the MAF sensor and the throttle plate is considered an uncalibrated air leak. Who is correct?

A) A only
B) B only
C) both A and B
D) neither A nor B

Answer 1

C

Question 2

What does the term injection pulse width refer to?

A) the off time of the fuel injector
B) the on time of the fuel injector
C) the voltage required to turn on the fuel injector
D) none of the above

Answer 2

B

Question 3

Low supply voltage at the fuel pump may result in low fuel pump volume.

Answer 3

True

Question 4

Intake manifolds made of glass fiber-reinforced nylon resin are lighter than older cast iron or aluminum manifolds, which improves fuel economy.

Question 5

Detergent added to gasoline helps to prevent deposits from building up on injector tips.

Question 6

The quantity or volume of fuel delivered to the cylinders by the fuel injectors is determined by:

A) the fuel pressure regulator
B) the length of time that the PCM supplies a ground signal to the injectors
C) the fuel pressure temperature sensor
D) the length of time that the PCM supplies a power signal to the MAF sensor

Question 7

A rich air/fuel ratio may be caused by low fuel pump pressure.

Question 8

The term injector pulse width refers to:

A) the off time of the fuel injector
B) the on time of the fuel injector
C) the voltage required to turn on the fuel injector
D) none of the above

Question 9

Low fuel pressure may be caused by a worn fuel pump or restricted fuel filter.

Question 10

A vehicle is brought in for a complaint of a rotten egg (sulphur) smell coming from the exhaust. The most likely cause(s) is/are:

A) insufficient fuel discharge
B) rich air/fuel ratio
C) both A and B
D) neither A nor B

Question 11

An idle speed control motor is sometimes referred to as a throttle kicker.

Question 12

The idle air control (AIC) motor controls idle speed under some but not all engine operating conditions.

Question 13

Electronic fuel injection systems, replacing older carburetor systems, have evolved to meet increasingly strict emissions regulations.

Question 14

During engine operation, the crankshaft position sensor identifies crankshaft position and:

A) direction of crankshaft rotation
B) fluctuations in air/fuel ratio
C) engine speed in rpms
D) camshaft speed

Question 15

In a returnless fuel system, no unused fuel is returned to the gas tank.

Question 16

A vacuum leak may cause the engine idle speed to be lower than specified.

Question 17

Technician A says that disconnecting the vehicle battery during diagnosis may erase the adaptive strategy from the PCM. Technician B says that a vacuum leak may be misdiagnosed as a fuel delivery problem. Who is correct?

A) A only
B) B only
C) both A and B
D) neither A nor B

Question 18

The term electronic fuel injection (EFI) may properly be applied to:

A) any electronic fuel injection system
B) only a gasoline direct injection system
C) only a multiport fuel injection system
D) only a sequential multiport fuel injection system

Question 19

Technician A says that the fuel system volume test can help to identify a restricted fuel filter. Technician B says that the fuel system pressure test is one of the first tests that should be performed during fuel system diagnosis. Who is correct?

A) A only
B) B only
C) both A and B
D) neither A nor B

Question 20

If the rpm signal is lost on an electronic fuel-injected vehicle, which of the following conditions will exist?

A) The ignition timing will be set to zero.
B) The PCM will go into backup mode base settings.
C) The engine will not run.
D) The vehicle will hesitate.

Question 21

What would the engine operational problem be on a vehicle with a defective fuel pump relay if the vehicle has an oil pressure switch wired in parallel to the fuel pump relay?

Question 22

How are SFI injectors controlled by the PCM?

Question 23

What do OBD II regulations require regarding a fuel system monitor?

Question 24

On a return-style fuel injection system, what could cause high fuel pressure, and what would the results be?

Question 25

How can after market exhaust system modifications reduce fuel efficiency and power?

Question 26

How does the PCM control the air/fuel ratio on fuel-injected engines?

Question 27

What effect could a plugged fuel system return line have on the fuel delivery system?

Question 28

Increasing injector pulse width has what effect on the air/fuel ratio?

Question 29

How does the PCM task manager monitor and correct fuel delivery?

Question 30

If a vehicle is not equipped with a mass air flow (MAF) sensor, how does the PCM determine the volume of the incoming air charge drawn into the combustion chamber?

Question 31

The PCM makes what assumption regarding the availability of fuel at the injectors?

Question 32

Why relieve the fuel pressure before disconnecting a fuel system component?

Question 33

What is the scavenging process?

Question 34

What are four components that are supplied voltage by the automatic shutdown (ASD) relay points in some vehicle systems?

Question 35

What is the purpose of the inertia switch in the fuel pump circuit?

Question 36

Why have many manufacturers integrated a returnless fuel system into their fuel system designs?

Question 37

What is the primary function of the fuel control system?

Question 38

What is one reason for the requirement of high system fuel pressures in port fuel-injected vehicles?

Question 39

How does the fuel system monitor treat one-trip and two-trip faults detected in the fuel delivery system?

Question 40

What is the most likely cause of a customer complaint of a rotten egg odor?