Fuel Supply Component Description. Oldsmobile Aurora 1999

For 1990-2009 cars only

Makes 🢒 Oldsmobile 🢒 1999 🢒 Aurora 🢒 Engine 🢒 Engine Controls - 4.0L and 4.6L 🢒 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: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

General Description

The fuel supply is stored in the fuel tank. An electric fuel pump, inside the modular fuel sender assembly (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 Operation Description .

On-Board Refueling Vapor Recovery System (ORVR)

The On-Board Refueling Vapor Recovery System (ORVR) is an on-board vehicle system to recover fuel vapors during the vehicle re-fueling operation. The flow of liquid fuel down to the fuel tank filler neck provides a liquid seal. The purpose of (ORVR) is to prevent re-fueling vapor from exiting the fuel tank filler neck.

The ORVR components include:

•

Fuel Tank

•	Fuel Tank Filler Pipe

•	EVAP Canister

•	Vapor Lines

•	Check Valve

•	Modular Fuel Sender (fuel tank pressure sensor located on modular fuel sender cover)

•	Fuel Limiter Vent Valve (FLVV)

•	Pressure Vacuum Relief Valve

•	Vapor Recirculation Line

•	Variable Orifice Valve

The On-board Refueling Vapor Recovery System (ORVR) is an on-board vehicle system designed to recover fuel vapors during the vehicle refueling operation. The flow of liquid fuel down the filler neck provides a liquid seal which prevents vapor from leaving the fuel system by transporting vapor to the EVAP canister for use by the engine. Listed below are the ORVR system components with a brief description of their operation:

•	Fuel Tank - contains the modular fuel sender, fuel limiter vent valve, and three rollover valves.

•	Fuel Filler Pipe - the pipe which carries fuel from the fuel nozzle to the fuel tank.

•	EVAP Canister - the EVAP canister receives refueling vapor from the fuel system, stores the vapor and releases the vapor to the engine upon demand.

•	Vapor Lines - transports fuel vapor from the tank assembly to the EVAP canister.

•	Check Valve - the check valve limits fuel "spit-back" from the fuel tank during the refueling operation by allowing fuel flow only into the fuel tank. This check valve is located at the bottom of the fuel filler pipe.

•	Modular Fuel Sender Assembly - this assembly pumps fuel to the engine from the fuel tank.

•	Fill Limiter Vent Valve (FLVV) - this valve acts as a shut-off valve located in the fuel tank and has the following functions:

-	Controls the fuel tank fill level by closing the primary vent from the fuel tank.

-	Prevents fuel from exiting the fuel tank via the vapor line to the canister.

-	Provides fuel-spillage protection in the event of a vehicle rollover by closing the vapor path from the tank to the EVAP canister.

•	Pressure/Vacuum Relief Valve - the pressure/vacuum relief valve provides venting of excessive fuel tank pressure and vacuum. The valve is located in the fuel filler neck on a plastic fuel tank.

•	Vapor Recirculation Line - The vapor recirculation line is used to transport vapor from the fuel tank to the top of the fill pipe during the refueling to reduce vapor loading to the Enhanced EVAP canister.

•	Variable Orifice Valve - The variable orifice valve regulates the amount of vapor allowed to enter the vapor recirculation line.

Enhanced EVAP System Operation

The basic Evaporative Emission (EVAP) Control System used on all vehicles is the charcoal canister storage method. This method transfers fuel vapor from the fuel tank to an activated carbon (charcoal) storage device canister to hold the vapors when the vehicle is not operating. When the engine is running, the fuel vapor is purged from the carbon element by intake air flow and consumed in the normal combustion process.

The EVAP purge valve allows manifold vacuum to purge the canister. The Powertrain Control Module (PCM) supplies a ground to energize the EVAP purge valve (purge ON). The EVAP purge valve control is Pulse Width Modulated (PWM) or turned ON and OFF several times a second.

The evaporative leak detection diagnostic strategy is based on applying vacuum to the EVAP system and monitoring vacuum decay. The fuel level sensor input to the PCM is used to determine if the fuel level in the tank is correct to run the EVAP diagnostic tests. To insure sufficient volume in the fuel tank to begin the various diagnostic tests, the fuel level must be between 15 percent and 85 percent. The PCM monitors system vacuum level via the fuel tank pressure sensor input.

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 EVAP charcoal canister. The service port is identified by a green colored cap. The port contains a schrader valve and fittings to allow the connection of the J 41413, evaporative pressure/purge diagnostic system. Refer to EVAP control system diagnosis for further information and diagnosis of the Enhanced EVAP system.

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 straps that are attached to the underbody. The fuel tank is made of plastic, 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.

The tank also contains a fuel vapor vent valve with roll-over protection. The vent valve also features a two phase vent calibration which increases fuel vapor flow to the canister when operating temperatures increase the tank pressure beyond an established threshold.

The fuel tank contains 3 rollover valves that prevents fuel from entering the fuel pipes in the event of a vehicle rollover. The rollover valves are not repairable.

Fuel Tank Filler Pipe


(1)	Fuel Tank Filler Pipe
(2)	Fuel Tank Filler Pipe Clamp
(3)	Fuel Tank

The fuel tank filler pipe carries dispensed fuel from the fuel nozzle to the fuel tank.

In order to prevent refueling with leaded fuel, the fuel tank filler pipe has a built-in restrictor and deflector.

A fuel tank filler pipe check-valve is attached to the fuel tank filler pipe and extends from the fuel tank inlet to the reservoir. The fuel tank filler pipe check-valve is located inside the fuel tank filler pipe check-valve tube and prevents fuel from splashing back out of the fuel tank filler pipe during re-fueling.

The opening in the restrictor will accept only the smaller unleaded gasoline fuel nozzle which must be fully inserted to bypass the deflector. The filler pipe is attached to the tank by a section of hose and two hose clamps.

Notice: Drain the fuel tank with a hose which has a 13 mm (0.5 in) or smaller diameter in order to prevent the drain hose from getting stuck inside the fuel tank filler neck pipe check valve. Damage to the check valve may result.

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 malfunction of the fuel system. A loose or incorrect fuel tank filler pipe cap can set a DTC.


(1)	Fuel Tank Filler Cap
(2)	Fuel Tank Filler Pipe
(3)	Fuel Filler Door

The fuel tank filler pipe is equipped with a screw-type fuel tank filler pipe cap. A built-in ratchet-type torque limiting device prevents overtightening. In order to install the cap, the cap must be turned clock-wise until a clicking noise is heard. This signals that the correct torque has been reached and the cap is fully seated. A fuel filler cap that is not fully seated can cause a malfunction in the emission system.

The fuel tank filler pipe cap has a pressure relief and vacuum relief. The fuel tank filler pipe cap has a tether connected to the fuel tank filler pipe.

Modular Fuel Sender Assembly


(1)	Fuel Tank Pressure Sensor
(2)	Fuel Pipes
(3)	Fuel Pump
(4)	External Fuel Sender Strainer
(5)	Fuel Level Sensor Assembly
(6)	Fuel Sender Cover

The modular fuel sender assembly is attached to the top of the fuel tank, and extends from the top of the fuel tank to the bottom.

The modular fuel sender assembly consists of the following major components: a fuel sender cover assembly, fuel pipes (above cover), a fuel pump, a fuel pump strainer, a fuel pump reservoir, an external fuel sender strainer, a ceramic card fuel level sensor assembly, and a fuel tank pressure sensor.

The fuel level sensor assembly 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. As the float position changes, the amount of current passing through the rheostat varies, thus changing the Gauge reading on the instrument panel.

The modular fuel sender assembly mounts to the opening of the plastic fuel tank. The spring loaded reservoir. The design provides:

•	Optimum fuel level in the integral fuel reservoir during all fuel tank levels and driving conditions.

•	Improved tank fuel level measuring accuracy.

•	Improved coarse straining and added pump inlet filtering.

•	More extensive internal fuel pump isolation for noiseless operation.

Modular Fuel Sender Fuel Flow


(1)	Fuel Feed
(2)	Fuel Return
(3)	Convoluted Fuel Tube (Flex Pipe)
(4)	Secondary Umbrella Valve
(5)	External Fuel Pump Strainer
(6)	Fuel Flow from External Strainer
(7)	Fuel Pump Strainer
(8)	Fuel Pump

The modular fuel sender assembly maintains optimum fuel level in the reservoir (bucket). Fuel entering the reservoir (bucket) is drawn in by:

•	The first stage of fuel flow is through the external strainer.

And/Or

•	The umbrella valve,

•	The return fuel pipe, whenever the level of fuel is below the top of the reservoir.

The fuel pump used in this system is part of the fuel sender assembly. The fuel pump lower connector assembly prevents the transmission of vibration and noise generated by the pump to the fuel tank.

Fuel enters the lower inlet port (secondary umbrella valve located inside of lower inlet port) of the fuel pump after being filtered by the external fuel strainer, and the fuel pump strainer. The initial function of the pump is to fill the reservoir.

The second stage separates vapor from the fuel in the pump. This vapor separation maximizes hot fuel handling and permits the vapor to return to the fuel tank at lower pressure and temperature. By creating positive fuel pressure, the pump then discharges the liquid fuel into the third stage of the pump. The pump outlet allows the fuel volume to flow through a check valve into the fuel pump flex pipe. The check valve seat is molded inside the connector body. The check valve body and retainer are assembled into the connector body. The check valve restricts fuel back flow.

After the fuel pump flex pipe, the fuel exits the assembly through the fuel feed output fitting on the molded cover. The cover also contains a fuel return provision which connects to one of three hollow support pipes.

Quick-connect pipe end fittings are molded onto the cover of the modular unit for ease of unit removal from the fuel tank. These quick-connect end fittings allow fuel feed and fuel return.

Electrical power to the fuel pump enters the unit by way of a connector which is attached to the cover. An internal wire harness and connector assembly connects to the fuel pump and level sensor. The modular design adds additional functions that improve accuracy and ensure constant, steady fuel supply under all conditions. All components and subassemblies of the modular sender attach to a common cover and access the fuel tank through a single opening. The modular fuel sender assembly is spring loaded to the bottom of the fuel tank. This bottom referencing permits continuous fuel pickup and accurate fuel level sensing. The reservoir assembly is the lower section of the modular unit which encases the fuel pump. A retainer attaches to the top of the reservoir. Fuel is captured and maintained in reservoir at a level sufficient to submerge the fuel pump.

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 Operation Description .

External Fuel Sender Strainer

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

The life of the fuel sender strainer is generally considered to be that of the fuel sender. The fuel sender 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 sender strainer is plugged, replace it with a new one.

Fuel Level Sensor Assembly

The fuel level sender 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 gauge. As the position of the float varies with fuel level, the rheostat produces a variable resistance between the fuel gauge. The fuel gauge 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.

In-Line Fuel Filter


(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 left side of the vehicle underbody in front of the fuel tank. 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 threaded fitting is sealed with an O-ring, which is replaceable. 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-pipe 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 inches ID for the fuel feed pipe, and 5/16 inches 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

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.

Fuel Feed and Fuel Return Pipes

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.

Fuel Pump Relay


(1)	Rear Relay Center
(2)	Rear Fuse Block

The fuel pump relay is located below the rear seat inside the fuse relay center. The fuel pump relay allows the fuel pump to be energized by the PCM. When the ignition is first turned On, the PCM energizes the fuel pump relay for two seconds. This allows the fuel pump to run for two seconds and build up fuel pressure for cranking. The PCM then waits for ignition reference pulses from the Ignition Control Module (ICM). Once the PCM sees references pulses, the PCM energizes the relay to run the fuel pump.

A faulty fuel pump relay may cause long cranking times and should set a DTC.