Description
Fuel Tank and Lines
System Operation
The fuel pump is a variable-speed rotary-vane type, which operates in a fuel module located in the right hand fuel tank compartment. A fuel transfer pump is located in the left hand compartment. Both components are secured by screw on plastic closure rings. The fuel pump module has an integral top plate for the external pipe work and electrical connectors.
Fuel level is maintained equally in the fuel tank compartments by circulating the fuel through internal crossover pipes via suction jet pumps which also serve to deliver a constant supply of fuel to the transfer pump and swirl pot assembly. High pressure fuel from the fuel pump is directed through the jet pump's orifice, creating a low pressure area to be formed around the orifice. The fuel is drawn into this low pressure area and directed into the swirl pot delivery pipes. This is achieved using the cross-over pipe from the left hand module and a direct link pipe from the right hand module.
Fuel is pumped from the fuel pump to the fuel rail via the parallel pressure relief valve and fuel filter. The parallel pressure relief valve contains two spring loaded valves, which operate in opposite directions.
The function of the valve is to
- Assist engine starting by retaining a pre-set fuel pressure in the supply pipe and fuel rail
- Limit fuel rail pressure due to temporary vapor increase in hot conditions
- Limit fuel rail pressure caused by sudden load changes, for example, a fully open to closed throttle transition
- Prevent leakage from the tank in the event that the fuel delivery pipe is severed
To meet ORVR (on-board refueling vapor recovery) requirements, the fuel tank and associated components are designed to minimize fuel vapor loss during refueling. This is achieved by preventing fuel vapor from the fuel tank venting directly to the atmosphere. Instead fuel vapor is directed into the EVAP (evaporative emission) canister where it is stored before being purged at intervals to the engine's intake manifold.
FUEL TANK
The fuel tank is a saddle type tank constructed of HDPE (high density polyethylene), a plastic blow molded material. The tank is located forward of the rear suspension and is mounted using two metal straps. The tank is a sealed unit with the only internal access being through the fuel pump module and transfer pump module flange apertures on the top of the tank.
The fuel pump module flange has a six pin external connector which provides the electrical connections for the fuel pump and level sensors. A quick release connector provides for the connection of the fuel feed pipe.
Each flange is fitted with a collar, clamp and seal which locate in the tank apertures. An arrow on each flange must be aligned between two molded lines on the tank, adjacent to the fuel pump module or transfer pump flange aperture, to obtain the correct pump orientation. A collar is located over each flange and is secured with a clamp. The flange, seal, collar and clamp arrangements meet the sealing requirements of LEV2 emissions.
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FUEL PUMP MODULE
The fuel pump is a variable speed rotary vane type. The supercharged variant incorporates a high flow rate pump. The pump is energized by the fuel pump relay which is located in the RJB (rear junction box) and the FPDM (fuel pump driver module) which is located under the RH floor pan above the rear suspension stabilizer bar. The relay and FPDM (fuel pump driver module) are controlled by the ECM (engine control module).
A fine mesh filter is located in the lower section of the pump module. This provides filtration to the fuel as it is drawn into the module.
The right hand fuel level sensor is mounted into the pump module housing.
FUEL LEVEL SENSORS
Two fuel level sensors are installed in either side of the saddle tank. One is mounted on the fuel pump module, the other is mounted on the transfer pump module in the other side of the fuel tank. The sensors are a MAPPS (magnetic passive position sensor) which provide a variable resistance to ground for the output from the fuel gage. The sensor is sealed from the fuel preventing contamination of the contacts, increasing reliability. The fuel level sensors are connected to the external electrical connector on the flange via the connector on the underside of the fuel pump module flange.
The sensor comprises a series of 51 film resistors mounted in an arc on a ceramic surface. The resistors are wired in series with individual contacts. A soft magnetic foil with 51 flexible contacts is mounted a small distance above the film resistors. A magnet, located below the ceramic surface, is attached to the sender unit float arm. As the float arm moves, the magnet follows the same arc as the film resistors. The magnet pulls the flexible contacts onto the opposite film resistor contacts forming an electrical circuit.
The film resistors are arranged in a linear arc with resistance ranging from 51.2 to 992.11 Ohms. The electrical output signal is proportional to the amount of fuel in the tank and the position of the float arm. The measured resistance is processed by the instrument cluster to implement an anti-slosh function. This monitors the signal and updates the fuel gage pointer position at regular intervals, preventing constant pointer movement caused by fuel movement in the tank due to cornering or braking.
A warning lamp is incorporated in the instrument cluster and illuminates when the fuel level is low.
The fuel level sender signal is converted into a CAN (controller area network) message by the instrument cluster as a direct interpretation of the fuel tank contents in liters. The ECM (engine control module) uses the CAN (controller area network) message to store additional OBD (on-board diagnostic) 'P' Codes for misfire detection when the fuel level is below a predetermined capacity.
JET PUMPS
The fuel system incorporates two jet pumps. The LH (left hand) jet pump is located on the fuel level sensor carrier on the LH (left hand) side of the fuel tank. The RH jet pump is located in the swirl pot below the fuel pump. Both jet pumps operate on a venturi effect created by the fuel at pump output pressure passing through the jet pump. This draws additional fuel from the tank through ports in the jet pump body, delivering additional fuel to the swirl pot. This function also serves to maintain an equal fuel level in the fuel tank compartments.
The LH (left hand) jet pump collects fuel from the LH (left hand) side of the tank and transfers it into the swirl pot on the RH (right hand) side of the tank.
The RH (right hand) jet pump collects fuel from below the swirl pot and transfers it to the upper section of the swirl pot. The action of the jet pumps ensures a constant supply of fuel to the swirl pot and fuel pump. Both jet pumps have a jet nozzle of 0.5 mm diameter.
FUEL FILTER
The fuel filter is of a conventional construction being that of a paper element sealed within a steel canister. The fuel filter is located behind the left-hand front fender splash shield.
FUEL FILLER PIPE ASSEMBLY
The fuel filler head is positioned at the rear of the vehicle, above the right hand rear wheel. The filler head is covered by a molded plastic cover which is electrically locked when the vehicle is locked. The filler cap is a conventional screw in type which is secured to the vehicle with a lanyard.
The filler head is an aluminum fabrication which is secured to the vehicle body by a bracket. The formed aluminum filler pipe locates in a short flexible hose attached to the tank which is secured with worm drive clamps.
NAS (North American Specification) vehicles feature connections and pipework on the rear of the filler head to allow for the functioning of the fuel tank EVAP (evaporative emission) system.