In order to prevent refueling with leaded fuel, the fuel tank filler pipe has a built-in restrictor and deflector. The fuel tank filler pipe is connected to the fuel tank filler extension by clamps.

Fuel Tank Filler Pipe Cap

Fuel Tank Filler Pipe Cap (Enhanced EVAP)

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

The fuel tank filler pipe is equipped with a threaded-type fuel tank filler pipe cap. The threaded part of the fuel tank filler pipe cap requires several turns counterclockwise before it can be removed. A built-in torque-limiting device prevents over tightening of the fuel tank filler pipe cap. In order to install the fuel tank filler pipe cap, turn the fuel tank filler pipe cap clockwise until at least 3 clicking noises are heard. The clicking noises signal that the correct torque has been reached and that the fuel tank filler pipe cap is fully seated. (H Car, VIN K Only) The Enhanced EVAP fuel tank pipe cap has a tether connected to the fuel filler pipe.

(H Car, VIN K Only). The fuel tank pressure sensor is used to detect small leaks in the evaporative emission system. The fuel tank pressure sensor is a three wire strain gauge sensor much like that of the common GM MAP sensor. However, this sensor has very different electrical characteristics due to its pressure differential design. The sensor measures the difference between the air pressure (or vacuum) in the fuel tank and the outside air pressure. The sensor mounts at the top of the fuel tank. A three wire electrical harness connects it to the Powertrain Control Module (PCM). The PCM supplies a five volt reference voltage and ground to the sensor. The sensor will return a voltage between 0.1 and 4.9 volts. When the air pressure in the fuel tank is equal to the outside air pressure, such as when the fuel fill cap is removed, the output voltage of the sensor will be 1.3 to 1.7 volts. Refer to Evaporative Emission Control System Diagnosis for further information and diagnosis of the enhanced EVAP system.

The fuel sender assembly (1) is attached to the top of the fuel tank, and extends from the top of the fuel tank to the reservoir.

The fuel sender assembly consists of the following major components: a fuel sender, a fuel pump (4), a fuel pump strainer (3), a ceramic card assembly (2), a fuel pulse dampener, and a roll-over valve.

The fuel sender is a ceramic card assembly that consists of the float, the wire float arm, the rheostat and the roll-over valve. The fuel level is sensed by the position of the float and float arm, which operates the 40-250 ohm rheostat.

The rheostat is mounted on the fuel sender and located in series with the voltage supply circuit from the fuel guage or body control module (BCM). As the position of the float varies with fuel level, the rheostat produces a variable resistance between the fuel guage or BCM and ground. The fuel guage converts this variable resistance into the fuel level reading display on the instrument panel.

An isolated circuit is used in this application. The isolated ground circuit uses a dedicated ground wire from the rheostat to the fuel sender connector. The isolated ground circuit is used to prevent erratic fuel level readings caused by a difference in voltage potential among vehicle ground points. An isolated ground terminal is connected electrically to one end of the ceramic card.

The roll-over valve is pressed into the EVAP pipe of the fuel sender and is not serviced separately. The roll-over valve prevents fuel from entering the engine compartment if the vehicle rolls over by shutting Off the EVAP pipe to the evaporative emission canister.

Fuel Sender Fuel Flow

A high pressure fuel pump is mounted to the fuel sender inside the fuel tank. The fuel is pumped to the engine at a specified flow and pressure through the fuel pump. Excess fuel is returned to the fuel tank by a return pipe. The fuel pump delivers a constant flow of fuel to the engine even during low fuel conditions and aggressive vehicle maneuvers.

The electric fuel pump operation is controlled by the Powertrain Control Module (PCM) through a fuel pump relay. Refer to Fuel Metering System Components and Electrical Diagnosis for further description and a wiring diagram of the fuel pump relay.

A woven plastic fuel pump strainer is attached to the lower end of the fuel pump in the fuel tank. The functions of the fuel pump strainer are to filter contaminants and to wick fuel.

The life of the fuel pump strainer is generally considered to be that of the fuel pump. 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, in which case the tank should be thoroughly cleaned, refer to Fuel System Cleaning . If the fuel pump strainer is plugged, replace it with a new one.

(VIN 1 Only). The L67 (supercharged) engine utilizes a two speed fuel pump control module. The fuel pump control module is located on the left-wheel house flange in the trunk. The fuel pump control module controls the fuel pump output depending on the MAP Sensor input received by the PCM.

When the ignition is first turned On, the PCM energizes the fuel pump relay which applies power to the fuel pump control module. Based on engine fuel demand, the PCM sends a signal to the fuel pump control module to change the fuel pump control module voltage output. The fuel pump will then pressurize the fuel system. The fuel pump relay will remain On as long as the engine is running or cranking and the PCM is receiving reference pulses. If no reference pulses are present the PCM de-energizes the fuel pump relay within two seconds after the ignition is turned On, or the engine is stopped. During high engine load situations, the PCM commands the fuel pump to run at high speed. Refer to Fuel Pump Electrical Circuit Diagnosis for further description and diagnosis of the fuel pump electrical circuit.

A fuel filter is used in the fuel feed pipe ahead of the fuel injection system. The fuel filter is mounted on the right side of the underbody. The fuel filter housing is constructed of steel (1) with a quick-connect fitting at the inlet of the fuel filter and a threaded fitting at the outlet of the fuel filter. The filter element is made of paper (2) and is designed to trap particles suspended in the fuel that may damage the injection system.

There is no service interval for in-line fuel filter replacement. Only replace the in-line fuel filter if it is restricted.

The fuel feed and fuel return pipes carry fuel from the fuel sender assembly to the fuel injection system and back to the fuel sender assembly.

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

Nylon fuel pipes are designed to perform the same job as the steel or flexible fuel pipes or hoses they replace. Nylon fuel pipes are constructed to withstand maximum fuel system pressure, exposure to fuel additives, and changes in temperature. There are two sizes used: 3/8" OD for the fuel feed pipe, and 5/16" OD for the fuel return pipe.

The fuel feed and fuel return pipes are assembled as a harness. Retaining clips hold the fuel pipes together and provide a means for attaching the fuel pipes to the vehicle. Sections of the fuel pipes that are exposed to chafing, high temperature or vibration are protected with heat resistant rubber hose and/or corrugated plastic conduit.

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

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

Quick-connect type fittings provide a simplified means of installing and connecting fuel system components. Depending on the vehicle model, there are two types of quick-connect fittings, each 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 the female connector, provide the fuel seal. Integral locking tabs or fingers hold the quick-connect fittings together.

The EVAP pipes are made of nylon and carry vapors from the fuel sender assembly and the evaporative emission canister purge valve to the evaporative emission canister.

(H Car, VIN K Only). The enhanced EVAP service port is located in the evaporative purge hose located between the purge solenoid and the canister. The service port is identified by a green colored cap. The port contains a schrader valve and fittings to allow connection of J 41413, evaporative pressure/purge diagnostic system. Refer to Evaporative Emission Control System Diagnosis for further information and diagnosis of the enhanced EVAP system.