Part 2

Fuel System Description


Fuel Sender Assembly

The fuel sender assembly is located in the fuel tank. The fuel sender assembly contains the electric fuel pump, the fuel level sensor, the fuel pressure regulator, and the fuel filter. Most of the fuel sender assembly components can be serviced separately.

Fuel Sender Assembly-FWD




1 - Fuel Sender Assembly - Upper Support
2 - Spring
3 - Retaining E-Clip
4 - Fuel Pressure Regulator O-rings
5 - Fuel Pressure Regulator
6 - Fuel Pump Strainer
7 - Fuel Sender Assembly - Lower Housing
8 - Fuel Level Sensor
9 - Fuel Pump Jet Tube
10 - Fuel Pump
11 - Fuel Pump O-ring
12 - Fuel Filter and Housing
13 - Fuel Pump Electrical Jumper Harness

Fuel Sender Assembly-AWD




1 - Fuel Tank Pressure (FTP) Sensor
2 - Fuel Sender Assembly Housing - Support
3 - Fuel Level Sensor
4 - Fuel Level Sender Wire Harness
5 - Fuel Pressure Regulator O-ring
6 - Fuel Pressure Regulator
7 - Fuel Pump Strainer
8 - Lower Cushion
9 - Fuel Sender Assembly End Cap - Support
10 - Retaining Clip
11 - Fuel Pump
12 - Fuel Pump O-ring
13 - Fuel Filter and Housing
14 - FTP Sensor Retaining Clip

Fuel Level Sensor





The fuel level sensor is part of the fuel sender assembly. The fuel level sensor (1) consists of a float (2), a float arm, and a variable resistor (1). The 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 (IPC) assembly. When the fuel level changes, the float position changes. The change in the float position increases or decreases the resistance reading of the variable resistor. The change in the resistance causes the position of the fuel gauge pointer to change.

The AWD fuel tank with the primary and secondary fuel supply chambers has two fuel level sensors, one for each chamber. The sensor in the secondary chamber sends fuel level information to the sensor in the primary chamber. Together, the two sensors provide the information used by the fuel gage in the instrument panel (IP).

Fuel Pump

The fuel pump is an electric pump that is controlled by the powertrain control module (PCM) through the circuit opening relay. When the PCM commands the fuel pump to operate, an impeller is driven by an electric motor in the pump assembly, causing the fuel in the tank to be drawn into the fuel pump inlet port. The fuel is then pumped under pressure through the fuel filter and the fuel pressure regulator, out to the fuel feed pipe and hoses to the fuel rail and the fuel injectors. The fuel pressure is maintained when the fuel pump is not running by a pressure control valve located within the pump.

Fuel Transfer Pump




1 - Inlet, pressurized fuel from regulator
2 - Venturi Orifice
3 - Outlet, fuel from regulator and secondary fuel chamber
4 - Fuel Tank Baffle
5 - Secondary Fuel Supply Inlet
6 - Fuel Transfer Pump

The fuel transfer pump (6) is a suction style pump that is used to move fuel from the secondary chamber of the fuel tank to the primary chamber of the fuel tank. Fuel enters the transfer pump (1) under pressure from the fuel pressure regulator. The fuel is forced thru a restriction (2) in the pump creating a venturi effect. At the point of the restriction, a low pressure area is created, which draws fuel into the pump (5) from the secondary chamber. The fuel from the secondary chamber (5) and the fuel from the fuel pressure regulator (1) mix together (3) and flow into a baffled area (4) of the primary chamber.

Fuel Pump Strainer

A fuel pump strainer is attached to the inlet end of the fuel pump and the fuel transfer pump pick-up tube, if equipped. The fuel pump strainer is made of woven plastic. The functions of the fuel pump strainer are to filter contaminants and to wick fuel. The fuel pump strainer is self-cleaning and normally requires no maintenance. Fuel stoppage at this point indicates that the fuel tank contains an abnormal amount of sediment or water. Clean the fuel tank and replace a plugged fuel pump strainer with a new strainer.

Fuel Filter

The fuel filter located in the fuel tank and is part of the fuel sender assembly. The fuel filter housing is constructed to withstand the maximum fuel system pressure, exposure to fuel additives, and changes in temperature. The filter element is made of paper and is designed to trap the particles in the fuel that may cause damage to the fuel injection system.

Fuel Pressure Regulator





The fuel pressure regulator is located in the fuel tank and is part of the fuel sender assembly. The fuel pressure regulator is a diaphragm-operated pressure relief valve consisting of a diaphragm, a spring, and a valve. The fuel pressure regulator is inserted into the fuel sender assembly and sealed with one or more O-rings (1). The fuel pressure regulator used with the composite fuel tank is a double O-ring (3) design, while the regulator in the steel fuel tank uses a single O-ring (2). A correctly calibrated fuel pressure regulator ensures that the fuel is delivered to the fuel injectors at the correct pressure.

Quick Connect Fittings

Quick connect style fuel fittings provide a simplified means of installing and connecting the fuel system components. Depending on the vehicle model, there are 2 types of quick connect fittings. Different types of fittings are used at different locations in the fuel system. Each type of quick connect fitting consists of a unique female connector and a compatible male fuel pipe end. O-rings located inside of the female connector provide a leak proof seal. Integral locking tabs or fingers hold the quick connect fittings together. A special tool is used to service the quick connect fittings.

Fuel Feed Pipes and Hoses

Warning

In order to Reduce the Risk of Fire and Personal Injury:

* If nylon fuel pipes are nicked, scratched or damaged during installation, Do Not attempt to repair the sections of the nylon fuel pipes. Replace them.
* When installing new fuel pipes, Do Not hammer directly on the fuel harness body clips as it may damage the nylon pipes resulting in a possible fuel leak.
* Always cover nylon vapor pipes with a wet towel before using a torch near them. Also, never expose the vehicle to temperatures higher than 115°C (239°F) for more than one hour, or more than 90°C (194°F) for any extended period.
* Before connecting fuel pipe fittings, always apply a few drops of clean engine oil to the male pipe ends. This will ensure proper reconnection and prevent a possible fuel leak. (During normal operation, the O-rings located in the female connector will swell and may prevent proper reconnection if not lubricated.)

The fuel feed and return pipes and hoses carry the fuel from the fuel tank to the fuel injectors. These pipes and hoses are attached to the underbody of the vehicle and should be inspected periodically for kinks or dents that could restrict the fuel flow.

Fuel Vapor Pipes and Hoses

The fuel vapor pipe and hoses carry the fuel vapors from the fuel tank to the evaporative emission (EVAP) canister located at the rear of the vehicle, ahead of the fuel tank. The fuel vapors are stored in the canister when the engine is not running. When the engine is running at the normal operating temperature and the accelerator pedal is depressed, the PCM will command the EVAP canister purge valve to open and allow the stored fuel vapors to be purged into the intake manifold where the vapors will be burned in the combustion process.

On-Board Refueling Vapor Recovery System (ORVR)





The on-board refueling vapor recovery (ORVR) system is an on-board vehicle system designed to recover fuel vapors during the vehicle refueling operation. Instead of allowing fuel vapors to escape to the atmosphere the ORVR system transports the vapor to the EVAP canister for use by the engine. The flow of liquid fuel down the fuel filler neck provides a liquid seal that prevents fuel vapor from leaving the fuel system. The ORVR system architecture varies from platform to platform. Some of the items listed below are optional depending on the platform application. The following is a list of all the ORVR system components with a brief description of their operation:

* The EVAP canister (1). The EVAP canister receives and stores refueling vapor from the fuel system. The EVAP canister releases the fuel vapor to the engine through the EVAP control system.
* The vapor lines (2). The vapor lines transport fuel vapor from the fuel tank assembly to the EVAP canister.
* The vapor recirculation line (3), if equipped. The vapor recirculation line transports fuel vapor from the fuel tank to the top of the fuel filler pipe during refueling in order to reduce the fuel vapor at the canister. The vapor recirculation line can be located inside the fuel filler pipe or outside of the fuel filler pipe.
* The variable orifice valve (4), if equipped. The variable orifice valve regulates the amount of vapor allowed to enter the vapor recirculation line.
* The fuel filler pipe (5). The fuel filler pipe carries fuel from the fuel dispensing nozzle to the fuel tank.
* The check valve (6). The check valve limits fuel spitback from the fuel tank during the refueling operation by allowing fuel flow only into the fuel tank. The check valve is located at the bottom of the fuel filler pipe or in the fuel tank filler neck.
* The fuel sender assembly (7). The fuel sender assembly pumps fuel to the engine from the fuel tank.
* The fill limiter vent valve (8). The fill limiter vent valve is typically located in the fuel tank and acts as a shut-off valve. The fill limiter vent valve performs the following functions:

- Controls the fuel tank fill level by closing the primary vent of the fuel tank.
- Prevents liquid fuel from exiting the fuel tank through the vapor line and entering the EVAP canister.
- Provides fuel-spillage protection in the event of a vehicle rollover by closing the vapor path from the tank to the EVAP canister.

* The pressure/vacuum relief valve (9), if equipped. The pressure/vacuum relief valve provides venting of excessive fuel tank pressure or vacuum. The pressure/vacuum relief valve is located in the fuel filler neck on a plastic fuel tank and in the fill limiter vent valve on a steel fuel tank.

Fill Limiter Vent Valve with AWD




1 - To EVAP Canister
2 - Vent Control Valve
3 - Atmosphere Chamber
4 - From Fuel Filler Pipe
5 - Tank Vapor Control Valve
6 - Fill Limiter Vent Valve (FLVV)

The fill limiter vent valve (FLVV) (6) used on the AWD fuel system is located on the fuel tank. The cross sectional view shows the path of fuel vapors leaving the fuel tank by passing thru the valve to the EVAP canister (1). When the fuel filler cap is removed during refueling, the atmosphere chamber (3) fills with atmospheric pressure that has entered thru the port (4) from the fuel filler pipe. The pressure in the atmosphere chamber (3) opens the port (1) to the EVAP canister by closing the vent control valve (2). Refueling causes the internal pressure in the fuel tank to increase, pushing fuel vapors into the FLVV (6) and out to the EVAP canister (1). When the fuel tank is full, the tank vapor control valve (5) closes, sealing off the port (1) to the EVAP canister.

Fill Limiter Vent Valve (FLVV) with
FWD




1 - FLVV
2 - Atmosphere Chamber
3 - EVAP Canister
4 - ORVR Vent Line Inlet Port
5 - Vapor Chamber
6 - Vent Control Valve

The FLVV (1) on the FWD vehicle is an integral part of the EVAP canister (3). The cross sectional view shows the path of fuel vapors passing thru the valve directly into the EVAP canister. When the fuel filler cap is removed during refueling, the atmosphere chamber (2) fills with atmospheric pressure that has entered thru the port from the fuel filler pipe. The pressure in the atmosphere chamber (2) opens the passage to the vapor chamber (5) by opening the vent control valve (6). Refueling causes the internal pressure in the fuel tank to increase, pushing fuel vapors into the ORVR port (4) and up thru the vent control valve (6) into the EVAP canister (3). When the fuel tank is full, the tank vapor control valve (5) closes, sealing off the passage into the EVAP canister.