Fuel System

Question 1

How does the Gasoline Injection System work? 2 steps.

Answer 1

1. An electric fuel pump generates pressure.
2. This pressure sends fuel from the fuel tank through the fuel rail and sprays the fuel into the engine’s intake manifold or port.

Question 2

List Five advantages of Gasoline Injection

Answer 2

1. There is improved atomisation
2. Better fuel distribution.
3. Smoother idle.
4. Improved fuel economy
5. Lower emissions.

Question 3

What is Atmospheric Pressure?

Answer 3

Atmospheric pressure is formed by the air surrounding the earth and is the pressure that the atmosphere exerts on the surface of the earth.

Question 4

What is Vacuum?

Answer 4

Vacuum is lower than atmospheric pressure, is sometimes called suction and is used by engines to pull fuel and air into the cylinders.

Question 5

What is the purpose of the Throttle Body?

Answer 5

The throttle body is art of the air intake system that controls and monitors the amount of air flowing into the engine via the butterfly valve, in response to the driver putting more or les pressure on the accelerator monitored by the throttle position sensor.

Question 6

Differentiate between Direct Injection and Indirect Injection

Answer 6

During indirect injection, fuel is sprayed into the intake manifold instead of in the combustion chamber. During direct injection, fuel is sprayed directly into the combustion chamber.

Question 7

List the three Gasoline Injection Controls.

Answer 7

1. Electronic Fuel Injection, 2. Hydraulic Fuel Injection, 3. Mechanical Fuel Injection.

Question 8

Explain briefly Sequential Injection

Answer 8

During sequential injection, the fuel injectors open one after the other in a way that matches the firing order of the engine’s cylinders.

Question 9

What are the Four Subsystems in the Electronic Fuel Injection System?

Answer 9

1. Fuel Delivery System.
2. Air Induction System.
3. Sensor System.
4. Computer Control System.

Question 10

List Five Fuel System Components.

Answer 10

1. Fuel Tank
2. Electric fuel pump
3. Fuel filter.
4. Fuel pressure regulator
5. Injectors.

Question 11

List Five sensors used by the ECU to control the Fuel System.

Answer 11

1. Knock Sensor
2. Airflow Sensor.
3. Oxygen Sensor.
4. Manifold Absolute Pressure Sensor.
5. Throttle Position Sensor

Question 12

Briefly explain how the Fuel Injector Operates.

Answer 12

A fuel injector is a solenoid - operated fuel valve.

1. When current flows from the ECU to the electrical terminals it produces an electric current
2. The current generates a magnetic field in the coil.
3. This magnetic field attracts the armature raising the ball or needle valve, opening the injector.

Question 13

List the Three Idle Speed Controls.

Answer 13

1. Fast Idle Thermo Valve
2. Idle air control motor.
3. Throttle Positioner.

Question 14

Explain Injector Pulse Width.

Answer 14

Pulse width is the length of time that the fuel injector is energised, which controls the amount of fuel injected. At wide open throttle, the ECU lengthens the injector pulse width to richen the mixture. At low load, the ECU shortens the injector pulse width creating a leaner mixture.

Question 15

Differentiate between Throttle Body Injection and Multiport Injection.

Answer 15

In throttle body injection, the injector nozzles are mounted in the throttle body assembly, where fuel sprays into the throttle body air horn and mixes with the air before it reaches the intake port.
In multiport injection, the injector nozzles are located near and spray fuel in the intake port towards the intake valve. Only air passes through the throttle body and it only mixes with fuel at the intake port. This also happens for each individual port.