The fuel tank stores the fuel supply. The electric fuel pump (6) attached to the primary fuel tank module (5), supplies fuel through an in-line fuel filter (15) to the fuel injection system. The fuel pump provides fuel at a higher rate of flow than is needed by the fuel injection system. The fuel pressure regulator (13), a part of the secondary fuel tank module (12), maintains the correct fuel pressure to the fuel injection system. A fuel return pipe (14) attaches between the in-line fuel filter and the secondary fuel tank module. When the fuel pressure exceeds the set point of the fuel pressure regulator, excess fuel flows to the low-pressure siphon jet pump (11) on the secondary fuel tank module. The return fuel creates a venturi action inside the siphon jet pump. The venturi action causes the fuel to be drawn from the secondary side of the fuel tank through the fuel transfer tube (10) to the primary side of the fuel tank. The electric fuel pump also supplies fuel to the high-pressure siphon jet pump (8), which is attached to the primary fuel tank module. The high-pressure siphon jet pump supplies fuel to the reservoir of the primary fuel tank module. The fuel pressure regulator also maintains fuel pressure in the fuel return pipe, which reduces the time to prime the low-pressure siphon jet pump.

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.

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

Notice: 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 engine control module (ECM) sends the fuel level percent via 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 ECM also monitors the fuel level input for various diagnostics.

The fuel pump 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. Excess fuel returns to the fuel tank through the fuel return pipe. 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 fuel pump flex pipe acts to dampen the fuel pulses and noise generated by the fuel pump.

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 is located on the fuel feed pipe, between the fuel pump and the fuel injectors. 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 feed pipe carries fuel from the fuel tank to the fuel injection system. The fuel return pipe carries fuel from the fuel filter back to the fuel tank. The fuel pipes consist of 3 sections:

Caution: 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 3 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 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 fuel pressure regulator attaches to the secondary fuel tank module. The fuel pressure regulator is a diaphragm relief valve. The diaphragm has fuel pressure on one side and regulator spring pressure on the other side. Fuel pressure is controlled by a pressure balance across the regulator. The fuel system pressure is constant and is not a function of engine load or manifold vacuum. A software bias compensates the injector on-time based on the signal from the MAP sensor.

The rapid opening and closing of the fuel injectors cause pressure fluctuation in the fuel rail. The result is that the amount of injected fuel will be more or less than the desired amount. Mounted on the fuel rail, the pulsation damper reduces these pressure fluctuations. When pressure suddenly begins to drop, the spring-loaded diaphragm extends slightly decreasing fuel rail volume. This will momentarily prevent fuel pressure from becoming too low.

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.