GM Service Manual Online
For 1990-2009 cars only

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 high density polyethlene. 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. A fuel tank filler pipe check-ball tube is attached to the fuel tank and extends from the fuel tank inlet to the reservoir. The fuel tank filler pipe check-ball is located inside the fuel tank filler pipe check-ball tube and prevents fuel from splashing back out of the fuel tank filler pipe during refueling.

Fuel Tank Filler Pipe Cap


Object Number: 12824  Size: SH

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 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.

Notice: Use a fuel tank filler pipe cap with the same features as the original when a replacement is necessary. Failure to use the correct fuel tank filler pipe cap can result in a serious malfunction of the fuel system.

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.


Object Number: 12823  Size: SH

The fuel sender assembly consists of the following major components: a fuel sender (6), a fuel pump (2), a fuel pump strainer (4), a deflector (3), and a roll-over valve (1).

The fuel sender 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 operate the 90 ohms 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 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 Pump

A high pressure turbine 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 Pump Electrical Circuit Diagnosis

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

In-Pipe Fuel Filter


Object Number: 12628  Size: SH

A fuel filter is used in the fuel feed pipe ahead of the fuel injection system. The fuel filter is mounted directly in front of the fuel tank. The fuel filter housing (1) 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 (2) 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-pipe fuel filter replacement. Only replace the in-pipe fuel filter if it is restricted.

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.

Nylon Fuel Pipes

Nylon fuel pipes are designed to perform the same job as the steel or rubber fuel lines they replace. Nylon pipes are constructed to withstand maximum fuel system pressure, exposure to fuel additives and changes in temperature. There are two sizes used: 3/8" ID for the fuel feed, and 5/16" ID for the fuel return and are used on the modular sender. Nylon fuel pipes are somewhat flexible and can be formed around gradual turns. However, if forced into sharp bends, nylon pipes will kink and restrict fuel flow. Also, once exposed to fuel, nylon 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 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.)

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 Pipe O-Rings

Fuel feed and return pipe threaded connections at the fuel rail and fuel filter are sealed with replaceable O-ring seals. These O-rings seals are made of special material, and should only be serviced with the correct service part.