1. Introduction to Electronic Fuel Systems
Topics covered in this presentation:
Types of Electronic Fuel Systems
Fuel Injection Timing, Open Loop and Closed Loop Modes
Wiring Diagrams and Schematics

2. Air fuel mixture control.
The term stoichiometric ratio describes the chemically correct air-fuel ratio necessary to achieve complete combustion of the fuel.
For simple and practical purposes it’s worked out in the following way: For a petrol engine the optimal operational value of the fuel /air ratio is 14.7 parts of air, to 1 part of fuel. By mass, that’s 14.7 kilograms of air to each kilogram of fuel.
Under ideal conditions, the air/fuel ratio is 14.7:1 when ignited will burn completely to produce exhaust emissions of CO2 and H2O.

3. Carburettors

4. Fuel Injectors Fuel strainer Electrical connector Solenoid winding
Return spring
Solenoid armature
Needle valve
Pintle
Seat
What is the purpose of no1?
To keep any dirt out of the injector that has made it past the filter.

5. Single and Multipoint EFI Systems
Fuel injection systems classified by point of injection.
ECU
Single Point Fuel Injection (Throttle Body Injection - TBI)
Injector located inside throttle body, sits on top of inlet manifold.
Fuel in
Air in
Throttle valve
Injector sprays fuel from above throttle valve.
Injector
Inlet manifold
Throttle body
ECU controls injector opening.
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6. Single point injection.

7. Single point injection

8. Question 1
In a single-point fuel injection system, where is the injector located?
A) In the inlet manifold
B) Next to the inlet valve
C) Before the air filter
Correct Answer = D
D) In the throttle body

9. Single and Multipoint EFI Systems
Multipoint Fuel Injection
ECU
Injector located in each branch of inlet manifold, below throttle valve.
Fuel in
Air in
Injectors x 4, x6, x8 etc.
Inlet manifold
Throttle valve
Injectors spray fuel directly into each port.
ECU controls opening of injectors.
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10. The injector spray finely atomised fuel into the throttle body or inlet ports depending on the system. The electromagnetic injection valves are actuated by the electronic control unit (ECU). The signals from the ECU are of a precise duration depending on the engines operating conditions with a range of about milliseconds. This open phase of the injector in known as the “injector pulse width”.

11. Multi point injection.

14. What is this components task?
To control the pressure in the fuel rail.  
The fuel pressure regulator consists of a spring loaded ball and diaphragm and is set to maintain a constant pressure difference between the fuel in the fuel rail and the inlet manifold (e.g. 2.5 bar). The pressure in the manifold depends on throttle opening so when the opening is small the high manifold vacuum encourages more fuel to leave the injector when it is open. When to manifold vacuum is low, low vacuum is applied to the diaphragm so the fuel pressure increases before it can lift the ball off its seat.

15. Fuel pressure regulator with vacuum applied

16. Fuel pressure Fuel pressure Atmospheric pressure
Typical fuel pressure – 3.0 bar without vacuum
Fuel pressure + vacuum = 3.0 bar
Atmospheric pressure
Fuel pressure
Intake manifold vacuum
Fuel pressure
Fuel pressure
Low
High
Intake manifold vacuum
Low pressure
High pressure
Injection volume
Same

18. State 2 places that the fuel pressure regulators can be located
Engine condition
Manifold vacuum
Typical fuel pressure
Idling
Very high
2.0 bar
Full throttle
Very low
2.5 bar
State 2 places that the fuel pressure regulators can be located
On the end of the fuel rail or in the tank with the pump.

19. Question 3
What controls the opening of the injectors in an EFI system?
A) The throttle valve
B) The air pressure
C) The ECU
Correct Answer = C
D) The pressure in the inlet manifold

20. Fuel Injection Timing
Describes when fuel is sprayed into the inlet manifold.
Intermittent (or modulated)
Injectors controlled independently of inlet valve position.
Timed (or sequential)
Injectors controlled in time with inlet valves.
Continuous
Injectors open all the time, fuel pressure is controlled.
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21. Question 4
In which method of fuel injection timing is the fuel supplied in time with the inlet valves?
A) Continuous
B) Sequential
C) Modulated
Correct Answer = B
D) Intermittent

22. Fuel Injector Opening Relationships
Simultaneous Injection (all together).
Sequential Injection (one at a time).
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23. Describe simultaneous injection timing.
Simultaneous injection means all the injectors fire together, delivering half the metered amount twice per engine cycle 
Describe sequential injection timing.
Sequential injection means the injectors’ fire in firing order sequence and the full metered fuel volume for the cycle is injected.

24. So Gasoline electronic Direct Injection System
An indirect injection system sprays fuel into the engine  intake  manifold.   Most  gasoline  injection systems are of this type.
Direct injection forces fuel into the engine combustion chambers. Diesel injection systems are direct type. So
Gasoline electronic Direct Injection System
is Classified as : multi-point and Direct injection systems

25. ECU Open & Closed Loop Operation
Engine cold, ECU operates in open loop mode.
Uses preprogrammed values to control engine.
Engine at operating temperature, ECU operates in closed loop mode.
It uses data from the oxygen and other sensors to control engine.
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26. Question 5 How many different modes does the ECU operate in? .
Correct Answer = 2

27. Typical Fuel System Sub-Systems
1. Fuel Supply System
Supplies clean fuel to fuel metering system (fuel pump, filters, pipes).
2. Air Supply System
Supplies controlled clean air to engine (air filter, ducting).
3. Fuel Metering System
Controls amount of fuel (and air) entering engine (injectors, pressure regulator, throttle valve).
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28. Fuel System Diagrams and Schematics
Fuel System Block Diagrams - 1
System and subsystem
blocks
Each block represents a system.
Lines represent connections between systems.
Arrows represent direction of flow.
Direction of
information
flow/control
Connection lines
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29. Fuel System Diagrams and Schematics
Fuel System Block Diagrams - 2
System and component
blocks
Connection lines
Each block represents a component.
Lines represent connections between systems.
Arrows represent direction of flow.
Direction of
information
flow/control
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30. Fuel System Diagrams and Schematics
Fuel System Schematic Diagrams
Wiring
Components
Fuel pipes
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31. Fuel System Diagrams and Schematics
Fuel System Wiring Diagrams
Wire size
Connector number
Component symbol
Wire colour
Wire
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32. Question 6
Fuel system wiring diagrams show wire size, wire colour and wire connector number. Is this true or false?
Answer True or False.
Correct Answer = T