Fuel Delivery and Air Induction: Description and Operation
DESCRIPTION
In a conventional fuel system, extra fuel is returned from the engine to the fuel tank through the pressure regulator. The Sephia has adopted a returnless fuel system which eliminates the fuel return line from engine to tank. The main reason for adopting this type of system is to lower fuel and fuel tank temperatures to reduce evaporative emissions.
FUEL DELIVERY MODULE
The fuel delivery module is installed in the fuel tank. The fuel delivery module consists of the following:
- Electric fuel pump
- Pressure regulator
- Fuel filter
- Fuel sender unit
- Fuel supply line connection
Electric fuel pump
The electric fuel pump is located in the fuel delivery module. It is mounted with and connected to the fuel sender unit.
The fuel pump is an electric pump controlled by the engine control module (ECM) through the fuel pump relay. The motor rotates an impeller within the pump assembly. This causes fuel within the fuel tank to be drawn into the fuel inlet port. Fuel is pumped out to fuel injectors under pressure through the fuel pipes and hoses.
Fuel pressure is retained when the fuel pump is not running by means of a one-way check valve located within the pump.
Fuel pressure regulator and injector
The fuel pressure is regulated by a fuel pressure regulator.
The injectors are directly supplied with battery voltage through the main relay. Fuel is metered and injected into the intake ports according to the signals received from the ECM.
When these injection signals are applied to the solenoid coil of the injector, the needle valve is pulled off its seat. Fuel is then injected into the intake port. The amount of fuel supplied to the engine depends on the duration of time the injectors stay open.
Fuel level sender assembly
The fuel level sender system consists of a float, float arm, and a variable resistor. Fuel level is measured by the position of the float in the fuel tank, and is indicated by a gauge in the instrument panel cluster assembly. When the fuel level changes, the float position changes.
The change in float position increases or decreases the resistance of the variable resistor. The change in resistance causes the position of the fuel gauge readout to change.
Fuel pipes and hoses
Fuel feed and return pipes (lines) and hoses carry fuel from the tank to the fuel rail. These pipes and hoses are attached to the underbody of the vehicle and must be inspected for kinks or dents which may restrict fuel flow.
Fuel vapor pipes and hoses carry fuel vapors from the fuel tank to the evaporative emissions canister located below the underbody. The fuel vapors are stored in the canister when the engine is not running. When the engine is running at normal operating temperature, and the accelerator pedal is depressed, the engine control module (ECM) will cause the evaporative emission solenoid purge valve to open and allow the stored fuel vapors to be purged into the intake manifold and be burned during the combustion process.
Fuel rail
The fuel rail supplies the necessary fuel to each individual fuel injector and is mounted to the intake manifold.
The fuel pressure regulator is no longer mounted to the fuel rail. It is now located in the fuel tank on the fuel delivery module.