The Fuel System is a returnless on-demand design. The fuel pressure regulator is a part of the primary fuel tank module, eliminating the need for a return pipe from the engine. A returnless Fuel System reduces the internal temperature of the fuel tank by not returning hot fuel from the engine to the fuel tank. Reducing the internal temperature of the fuel tank results in lower evaporative emissions.

An electric turbine style fuel pump attaches to the primary fuel tank module inside the fuel tank. The fuel pump supplies high pressure fuel through the fuel filter, past the fuel pressure regulator, and through the fuel feed pipe to the Fuel Injection System. The fuel pressure regulator has a T-joint that diverts the needed fuel to the fuel rail with the unused fuel dropping back into the reservoir of the primary fuel tank module. The primary fuel tank module contains a reverse flow check valve. The check valve and the fuel pressure regulator maintain fuel pressure in the fuel feed pipe and the fuel rail in order to prevent long cranking times.

The primary fuel tank module also contains a primary jet pump and a secondary jet pump. Fuel pump flow loss, caused by vapor expulsion in the pump inlet chamber, is diverted to the primary jet pump and the secondary jet pump through a restrictive orifice located on the pump cover. The primary jet pump fills the reservoir of the primary fuel tank module. The secondary jet pump creates a venturi action which causes the fuel to be drawn from the secondary side of the fuel tank, through the fuel transfer pipe, to the primary side of the fuel tank.

The fuel tank stores the fuel supply. The fuel tank is located in the rear of the vehicle. The fuel tank is held in place by 2 metal straps that attach to the under body of the vehicle. The fuel tank is molded from high-density polyethylene.

In order to provide space for a driveshaft though the center area of the tank, the fuel tank is a saddle configuration. Because of the saddle shape of the tank two fuel tank modules are required. The primary fuel tank module is located on the right side of the tank. The secondary fuel tank module is located on the left side of the tank.

The fuel fill pipe has a built-in restrictor in order to prevent refueling with leaded fuel.

Caution: If a fuel tank filler cap requires replacement, use only a fuel tank filler cap with the same features. Failure to use the correct fuel tank filler cap can result in a serious malfunction of the fuel and EVAP system.

The fuel fill pipe has a tethered fuel filler cap. A torque-limiting device prevents the cap from being over-tightened. To install the cap, turn the cap clockwise until you hear audible clicks. This indicates that the cap is correctly torqued and fully seated. A fuel filler cap that is not fully seated may cause a malfunction in the Emission System.

The primary fuel tank module is located inside of the right side of the fuel tank. The primary fuel tank module consists of the following major components:

The secondary fuel tank module is located inside of the left side of the fuel tank. The secondary fuel tank module consists of the following major components:

The fuel level sensor consists of a float, a wire float arm, and a ceramic resistor card. The position of the float arm indicates the fuel level. The fuel level sensor contains a variable resistor which changes resistance in correspondence with the position of the float arm. The control module sends the fuel level information via the CAN serial data to the body control module (BCM). The instrument panel cluster (IPC) displays the fuel level as determined by the BCM. This information is used for the IPC fuel gage and the low fuel warning indicator, if applicable. The control module also monitors the fuel level input for various diagnostics.

The fuel pump (2) is mounted in the primary fuel tank module reservoir. The fuel pump is an electric high-pressure pump. Fuel is pumped to the fuel injection system at a specified flow and pressure. The fuel pump delivers a constant flow of fuel to the engine even during low fuel conditions and aggressive vehicle maneuvers. The control module controls the electric fuel pump operation through a fuel pump relay.

The primary jet pump (1) is located in the primary fuel tank module. Fuel pump flow loss, caused by vapor expulsion in the pump inlet chamber, is diverted to the primary jet pump and the secondary jet pump (2) through a restrictive orifice located on the pump cover. The primary jet pump fills the reservoir of the primary fuel tank module.

The secondary jet pump (1) creates a venturi action which causes the fuel to be drawn from the secondary side of the fuel tank, through the transfer pipe, to the primary side of the fuel tank.

The fuel strainer attaches to the lower end of the primary fuel tank module. The fuel strainer is made of woven plastic. The functions of the fuel strainer are to filter contaminants and to wick fuel. The fuel strainer normally requires no maintenance. Fuel stoppage at this point indicates that the fuel tank contains an abnormal amount of sediment or contamination.

The fuel filter (1) is located in the primary fuel tank module. The paper filter element traps particles in the fuel that may damage the fuel injection system. The filter housing is made to withstand maximum fuel system pressure, exposure to fuel additives, and changes in temperature.

The fuel pressure regulator is integrated into the fuel filter cover on the primary fuel tank module. The fuel pressure regulator uses a spring with a preset tension and a stainless steel ball inserted into a precision ground seat in order to regulate fuel pressure. This type of fuel pressure regulator is not serviceable.

The fuel feed pipe carries fuel from the fuel tank to the fuel injection system. The fuel pipe consists of 3 sections:

Warning: In order to reduce the risk of fire and personal injury observe the following items:

Nylon pipes are constructed to withstand maximum fuel system pressure, exposure to fuel additives, and changes in temperature. The following 2 sizes of nylon pipes are used:

Heat resistant rubber hose or corrugated plastic conduit protect the sections of the pipes that are exposed to chafing, high temperature, or vibration.

Nylon fuel pipes are somewhat flexible and can be formed around gradual turns under the vehicle. However, if nylon fuel pipes are forced into sharp bends, the pipes kink and restrict the fuel flow. Also, once exposed to fuel, nylon pipes may become stiffer and are more likely to kink if bent too far. Take special care when working on a vehicle with nylon fuel pipes.

Quick-connect fittings provide a simplified means of installing and connecting fuel system components. The fittings consist of a unique female connector and a compatible male pipe end. O-rings, located inside the female connector, provide the fuel seal. Integral locking tabs inside the female connector hold the fittings together.

O-rings seal the threaded connections in the fuel system. The fuel system O-ring seals are made of special material. Service the O-ring seals with the correct service part.

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 evaporative emission (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 fuel rail assembly attaches to the engine intake manifold. The fuel rail assembly performs the following functions:

The fuel injector assembly is a solenoid device controlled by the control module that meters pressurized fuel to a single engine cylinder. The control module energizes the high-impedance, 12 ohm, injector solenoid (4) to open a normally closed ball valve (1). This allows fuel to flow into the top of the injector, past the ball valve, and through a director plate (3) at the injector outlet. The director plate has machined holes that control the fuel flow, generating a spray of finely atomized fuel at the injector tip. Fuel from the injector tip is directed at the intake valve, causing the fuel to become further atomized and vaporized before entering the combustion chamber. This fine atomization improves fuel economy and emissions.

The control module monitors voltages from several sensors in order to determine how much fuel to give the engine. The control module controls the amount of fuel delivered to the engine by changing the fuel injector pulse width. The fuel is delivered under one of several modes.

When the ignition is first turned ON, the control module energizes the fuel pump relay for 2 seconds. This allows the fuel pump to build pressure in the fuel system. The control module calculates the air/fuel ratio based on inputs from the engine coolant temperature (ECT), manifold absolute pressure (MAP), and throttle position (TP) sensors. The system stays in starting mode until the engine speed reaches a predetermined RPM.

If the engine floods, clear the engine by pressing the accelerator pedal down to the floor and then crank the engine. When the TP sensor is at wide open throttle (WOT), the control module reduces the fuel injector pulse width in order to increase the air to fuel ratio. The control module holds this injector rate as long as the throttle stays wide open and the engine speed is below a predetermined RPM. If the throttle is not held wide open, the control module returns to the starting mode.

The run mode has 2 conditions called Open Loop and Closed Loop. When the engine is first started and the engine speed is above a predetermined RPM, the system begins Open Loop operation. The control module ignores the signal from the heated oxygen sensor (HO2S). The control module calculates the air/fuel ratio based on inputs from the ECT, MAP, and TP sensors. The system stays in Open Loop until meeting the following conditions:

Specific values for the above conditions exist for this engine, and are stored in the electrically erasable programmable read-only memory (EEPROM). The system begins Closed Loop operation after reaching these values. In Closed Loop, the control module calculates the air/fuel ratio, injector ON time, based upon the signal from various sensors, but mainly from the HO2S. This allows the air/fuel ratio to stay very close to 14.7:1.

When the driver pushes on the accelerator pedal, air flow into the cylinders increases rapidly. To prevent possible hesitation, the control module increases the pulse width to the injectors to provide extra fuel during acceleration. This is also known as power enrichment. The control module determines the amount of fuel required based upon the TP, the ECT, the MAP, and the engine speed.

When the driver releases the accelerator pedal, air flow into the engine is reduced. The control module monitors the corresponding changes in the TP and the MAP. The control module shuts OFF fuel completely if the deceleration is very rapid, or for long periods, such as long, closed-throttle coast-down. The fuel shuts OFF in order to prevent damage to the catalytic converters.

When the battery voltage is low, the control module compensates for the weak spark delivered by the ignition system in the following ways:

The control module cuts OFF fuel from the fuel injectors when the following conditions are met in order to protect the powertrain from damage and improve driveability:

The control module controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. The control module monitors the HO2S signal voltage while in Closed Loop and regulates the fuel delivery by adjusting the pulse width of the injectors based on this signal. The ideal fuel trim (FT) values are around 0 percent for both short and long term FT. A positive FT value indicates the control module is adding fuel in order to compensate for a lean condition by increasing the pulse width. A negative FT value indicates that the control module is reducing the amount of fuel in order to compensate for a rich condition by decreasing the pulse width. A change made to the fuel delivery changes the long and short term FT values. The short term FT values change rapidly in response to the HO2S signal voltage. These changes fine tune the engine fueling. The long term FT makes coarse adjustments to fueling in order to re-center and restore control to short term FT. A scan tool can be used to monitor the short and long term FT values. The long term FT diagnostic is based on an average of several of the long term speed load learn cells. The control module selects the cells based on the engine speed and engine load. If the control module detects an excessively lean or rich condition, the control module will set a FT DTC.