Fuel Supply Component Description. Buick LeSabre 1999

For 1990-2009 cars only

Makes 🢒 Buick 🢒 1999 🢒 LeSabre 🢒 Engine 🢒 Engine Controls - 3.8L 🢒 Fuel Supply Component Description

Caution: This vehicle is equipped with Supplemental Inflatable Restraint (SIR). Refer to the Cautions in the On-Vehicle Service and the SIR Component and Wiring Location view in the Supplemental Inflatable (SIR) System before any performing service on or around SIR components or wiring. Failure to follow the Cautions could result in possible air bag deployment, personal injury, or otherwise unneeded SIR system repairs.

Notice: Always use the correct fastener in the proper location. When you replace a fastener, use ONLY the exact part number for that application.

The applicable service procedure will identify, where necessary, those fasteners that must be replaced after removal; or those fasteners that require the use of thread locking compound or thread sealant.

UNLESS OTHERWISE SPECIFIED, do not use supplemental coatings (paints, greases, or other corrosion inhibitors) on threaded fasteners or fastener joint interfaces. Generally, such coatings adversely affect the fastener torque and the joint clamping force, and may damage the fastener.

When you install fasteners, use the correct tightening sequence and specifications.

Following these instructions can help you avoid damage to parts and systems.

Notice: Always re-attach the fuel lines and fuel filter with all original type fasteners and hardware.

Do not repair sections of fuel pipes.

General Description

The fuel supply is stored in the fuel tank. An electric fuel pump, attached to the fuel sender (inside the fuel tank) pumps fuel through an in-line filter to the fuel injection system. The fuel pump is designed to provide fuel at a pressure above the regulated pressure needed by the fuel injectors. A fuel pressure regulator keeps fuel available to the fuel injectors at a regulated pressure. Unused fuel is returned to the fuel tank by a separate pipe. For further information on the fuel injection system, refer to Fuel Metering System Component Description .

Unleaded fuel must be used with all gasoline engines for proper emission control system operation. Using unleaded fuel will also decrease spark plug fouling and extend engine oil life. Leaded fuel can damage the emission control system, and its use can result in loss of emission warranty coverage. All vehicles with gasoline engines are equipped with an evaporative emission system that minimizes the escape of fuel vapors to the atmosphere. For information regarding this system, refer to: Evaporative Emission Control System Diagnosis .

Fuel Tank


(1)	Fuel Tank

The fuel tank is used to store fuel for the vehicle. The tank is located in the rear of the vehicle and is held in place by two metal straps that are attached to the underbody. The fuel tank is made of steel and is coated internally with a special corrosion inhibitor. Due to the internal coating of the fuel tank, the fuel tank is not repairable. The fuel tank shape includes a reservoir in order to maintain a constant supply of fuel around the fuel pump strainer during low fuel conditions and aggressive vehicle maneuvers.

Fuel Tank Filler Pipe


(1)	Fuel Tank Filler Extension
(2)	Clamps
(3)	Fuel Filler Pipe

In order to prevent refueling with leaded fuel, the fuel tank filler pipe has a built-in restrictor and deflector. The opening in the built-in restrictor will only accept the smaller unleaded gasoline fuel nozzle which must be fully inserted to bypass the deflector. The fuel tank filler pipe is connected to the fuel tank filler extension by clamps.

Fuel Tank Filler Pipe Cap

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 a clicking noise is heard. The clicking noise signals that the correct torque has been reached and that the fuel tank filler pipe cap is fully seated. The Enhanced EVAP fuel tank pipe cap has a tether connected to the fuel filler pipe.

Fuel Tank Vapor Pressure Sensor

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.

Fuel Sender Assembly


(1)	Fuel Pump
(2)	Fuel Pump Strainer
(3)	Fuel Level Sensor
(4)	Fuel Sender Assembly

The fuel sender assembly 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, a fuel pump strainer, a fuel level sensor assembly, a fuel pulse dampener, and a roll-over valve.

Fuel Sender

The fuel level sensor is a ceramic card assembly that consists of the float, the wire float arm, and the rheostat. The fuel level is sensed by the position of the float and float arm, which operates the 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 (Typical)

Fuel Pump


(1)	Fuel Pump
(2)	Fuel Pump Strainer
(3)	Fuel Pulse Dampener

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 Component Description and Electrical Diagnosis for further description and a wiring diagram of the fuel pump relay.

Fuel Pump Strainer

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.

Fuel Pump Control Module

(VIN 1 Only). The 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.

Fuel Pump Relay


(1)	Instrument Panel Power Distribution Center
(2)	Fuel Pump Relay

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.

In-Line Fuel Filter (Typical)


(1)	Fuel Filter Housing
(2)	Fuel Filter Element

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 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 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.

Nylon Fuel Pipes

Caution: 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.)

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 inch ID for the fuel feed pipe, and 5/16 inch ID 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.

Quick-Connect Fittings

Caution: 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.

•

Quick-connect type fittings provide a simplified means of installing and connecting fuel system components. Depending on the vehicle model, there are metal and plastic 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.

Enhanced Evaporative Emission (EVAP) Service Port

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.