Fuel Supply System. Cadillac Concours 1997

For 1990-2009 cars

## Fuel Supply System System Components

### Fuel Tank

(1) | Modular Fuel Sender -- Fuel Level Sender
(2) | Fuel Tank Strap Bolt
(3) | Fuel Tank Straps
(4) | Fuel Tank

The fuel storage tank is made of high density polyethylene and is located in front of the rear wheels. It is held in place by two metal straps attached to the under body of the vehicle. The tank shape includes a sump to maintain a constant supply of fuel around the fuel pump strainer during low fuel conditions or aggressive 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.

### Fuel Tank Filler Pipe

(1) | Fuel Filler Pipe
(2) | Fill Hose
(3) | Clamps
(4) | Fuel Tank

To help prevent refueling with leaded fuel, the fuel filler pipe has a built-in restrictor and deflector. 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. The tank is vented during filling by an internal vent tube inside the filler pipe.

### Fuel Filler Cap

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

The fuel tank filler pipe is equipped with a turn to vent screw on type cap which incorporates a ratchet action to prevent over-tightening. The filler cap is located inside the fuel filler door.

The turn to vent feature allows fuel tank pressure relief prior to removal. Instructions for proper use are imprinted on the cap cover. A vacuum safety relief valve is incorporated into this cap.

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.

### Modular Fuel Sender - Fuel Level Sensor

(1) | Fuel Sender Cover Assembly
(2) | Fuel Feed and Return Quick-Connects
(3) | Fuel Sender Support Assembly
(4) | Reservoir
(5) | Fuel Sender Strainer Assembly
(6) | Fuel Level Sensor Assembly

The modular fuel sender assembly mounts to the threaded opening of the plastic fuel tank with a multi-lipped seal and threaded retainer (nut). The spring loaded reservoir, containing the exterior inlet strainer, electric fuel pump and pump strainer, maintains contact with the tank bottom. This 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.

The modular fuel sender assembly consists of the following major components: A fuel sender cover assembly, a fuel sender, fuel pipes (above cover), a fuel sender support assembly, a fuel pump, a fuel pump strainer, a fuel pump reservoir, a fuel sender strainer, and a fuel level sensor assembly.

### Modular Fuel Sender - Fuel Flow

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

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 the fuel pump through the external strainer.

| And/Or

• | The secondary umbrella valve,

| Or

• | 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 electric 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.

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 pump.

A rubber bumper (pad) is assembled between the bottom of the reservoir and the fuel sender strainer. This promotes noise isolation by acting as a buffer between the reservoir bottom and the fuel tank and provides a fastening mechanism for the fuel level sensor assembly to the reservoir.

Two 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.

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.

### Modular Fuel Sender Serviceable Components

(1) | Fuel Sender Strainer
(2) | Fuel Level Sensor Assembly

The serviceable components on the Modular fuel sender are the fuel sender strainer, and the fuel level sensor assembly.

The strainer acts as a coarse filter to: filter contaminants, separate water from fuel, and to provide a wicking action that helps draw fuel into the fuel pump.

Fuel stoppage at the strainer indicates that the fuel tank contains an abnormal amount of sediment or water. Therefore, the fuel tank should be removed, cleaned, and the filter strainer replaced. Refer to Fuel System Cleaning .

### Fuel Level Sender Assembly

The fuel level sender attaches to the outside of the reservoir and measures the amount of fuel in the tank. The fuel level sender consists of the following components: the rheostat, the float, and the float arm. The assembly converts changes in the fuel level to a variable electrical signal used to drive a gauge in the instrument cluster. An electrical harness attached to the fuel sender cover connects the rheostat to the vehicle's wiring harness.

### Fuel Pump

The electric fuel pump is a fuel pump located inside the modular fuel sender. The electric fuel pump operation is controlled by the PCM through two fuel pump relays.

A rubber bumper (pad), is assembled between the bottom of the reservoir and the fuel sender strainer. This promotes noise isolation by acting as a buffer between the reservoir bottom and the fuel tank and provides a fastening mechanism for the fuel level sensor assembly to the reservoir.

### In-Line Fuel Filter

A in-line filter is used in the fuel feed pipe ahead of the fuel injection system. The filter element is made of paper, and is designed to trap particles in the fuel that may damage the injection system. Quick-connect type fittings are used at both ends of the filter.

### Powertrain Control Module

(1) | PCM Connector
(2) | Powertrain Control Module
(3) | PCM Isolater
(4) | Air Inlet Housing
(5) | PCM Connector

The PCM receives data from various information sensors, determines the required fuel and idle speed values and then controls the IAC valve, eight fuel injectors, and spark advance to maintain the optimum performance and driveability under all driving conditions. For more information on the PCM, refer to Powertrain Control Module Diagnosis .

### Fuel Pump Relay

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.

### Fuel and EVAP Pipe - Engine Compartment

(1) | EVAP Pipe
(2) | Fuel Feed Pipe
(3) | Fuel Return Pipe
(4) | Fuel Return Pipe Retainer
(5) | Fuel Feed Pipe Retainer

### Rear Fuel and EVAP Pipes and EVAP Canister

(1) | EVAP Canister Pipes
(2) | EVAP Canister
(3) | EVAP Canister Filter

The fuel feed, return, pipes carry fuel to and from the fuel rail as part of the fuel delivery system. The EVAP pipes carries fuel vapors for the EVAP components. Retaining clips hold the pipes together and provide a means for attaching the pipes to the vehicle. Quick-connect type fittings are used at the ends of the fuel feed and return and at the in-line fuel filter. They are described below. Sections of the pipes that are exposed to chafing, high temperature or vibration are protected with heat resistant rubber hose and/or coextruded conduit.

### Nylon Fuel Pipes

Nylon fuel pipes are designed to perform the same function as the steel or rubber fuel pipes they replace. Nylon pipes are constructed to withstand maximum fuel system pressure, exposure to fuel additives, and changes in temperature. Both fuel feed and fuel return pipe size is 5/16 OD. The EVAP pipe from tank to canister size is 1/4 OD and from canister to engine is 5/16 OD. The vacuum signal pipe is 1/4 ID. Nylon fuel pipes are somewhat flexible and can be formed around gradual turns under the vehicle. 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 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:

• | 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. There are metal collar and plastic types of quick-connect fittings used at different locations in the fuel system. Each type consists of a unique female socket and a compatible male connector. O-rings, located inside the female socket, provide the fuel seal. Integral locking tabs or fingers hold the fittings together. The quick-connect fittings used at the fuel filter and other connections at the rear of the vehicle have hand releasable locking tabs. The fittings used at the engine fuel pipes have locking tabs that require a special tool to release.

## Fuel Supply System Specifications

### Fuel

The fuel must meet ASTM Standard: D4814 (U.S.), CGSB 3.5-M93 (Canada).

### Octane Requirements

Minimum Octane requirement: 91 [(R+M)/2] (pump) octane where R=research octane number and M=motor octane number.

### Gasoline with Alcohol

Notice: Do Not spill fuel containing alcohol on the vehicle. Alcohol can cause damage to the paint finish and the trim.

### Methyl Tertiary-Butyl Ether (MTBE)

Fuel containing Methyl Tertiary-Butyl Ether (MTBE) may be used, providing there is no more than 15% alcohol by volume.

### Ethanol

Fuel containing ethanol (ethyl) or grain alcohol may be used, providing that there is no more than 10% ethanol alcohol by volume.

### Methanol

Notice: Do not use fuels containing methanol in order to prevent damage and corrosion to the fuel system.

### Methylcyclopentadienyl Manganese Tricarbonyl (MMT)

If a vehicle is certified to meet California Emission Standards (indicated on the under-hood tune-up label), it is designed to operate on fuels that meet California specifications. If such fuels are not available in states adopting California emissions standards, a vehicle will operate satisfactorily on fuels meeting federal specifications, but emission control system performance may be affected. The malfunction indicator lamp on the instrument panel may turn on. The vehicle may also fail a smog-check test.

Some gasolines that are not reformulated for low emissions contain an octane-enhancing additive called methylcyclopentadienyl manganese tricarbonyl (MMT). General Motors does not recommend the use of such gasolines. If fuels containing MMT are used, spark plug life may be reduced, and emission control system performance can be affected. The malfunction indicator lamp on the instrument panel can turn on.

To provide cleaner air, all gasolines are now required to contain additives that will help prevent deposits from forming in the engine and fuel system. These additives will allow the emission system to function properly. Therefore, there does not need to be anything added to the fuel. In addition, gasolines containing oxygenates, such as ethers and ethanol, and reformulated gasolines may be available in the area to help clean the air. General Motors recommends that the above mentioned gasolines be used if they comply with specifications described earlier.