Fuel Tank and Lines
Fuel Tank and Lines
COMPONENT LOCATION
INTRODUCTION
The fuel tank and lines is an electronically controlled returnless system that delivers a continuous supply of LP fuel to the fuel charging and control system on the engine. For additional information, refer to Fuel Charging and Controls Fuel Charging and Controls
For additional information, refer to Fuel Charging and Controls Fuel Charging and Controls
The fuel tank and lines has:
- A fuel tank.
- A FPDM (fuel pump driver module).
- A fuel filler pipe.
- A vent pipe.
- A fuel delivery line.
- A fuel LP sensor.
FUEL TANK
The fuel tank is a saddle type tank made of upper and lower pressings of stainless steel. Two baffle plates are installed in the fuel tank to reduce fuel surge.
Two metal straps attach the fuel tank to the underside of the vehicle, just forward of the rear suspension. A heat shield is attached to the metal straps and to two brackets on the underside of the fuel tank. Isolator pads are bonded to the top of the fuel tank at the contact points between the fuel tank and the vehicle.
Incorporated into the fuel tank are:
- A pump module.
- A mounting flange.
- A PVV.
- A LVS and related vent pipes.
- A remote pump housing and related fuel pipes.
- Two fuel level sensors.
- A fuel filler check valve.
Pump Module
The pump module takes fuel from both sides of the fuel tank and supplies it to the fuel delivery line via the PVV and the mounting flange. The pump module is mounted in the RH (right-hand) side of the fuel tank, on a bayonet fitting welded to the bottom of the fuel tank.
A swirl pot is integrated into the base of the pump module housing. A 60 micron filter is attached to the swirl pot inlet at the base of the housing.
The fuel pump is an electric, variable speed, vane pump installed in the top of the housing. The pump has a maximum rated flow of 234 liters/hour (61.82 US gallons/hour) at 12.2 V and 4.5 bar (65.3 lbf/in.2).
The inlet of the fuel pump is located in the center of the swirl pot. Pipes connect the two outlet ports of the fuel pump to the PVV and to a jet pump on top of the housing. The jet pump draws fuel from the LH (left-hand) side of the fuel tank through a suction pipe connected to the remote pump housing. A 'spider trap' in the remote pump housing prevents the ingress of larger pieces of debris.
Operation of the fuel pump is controlled by the FPDM (fuel pump driver module). The fuel pump is connected to the FPDM (fuel pump driver module) via an electrical connector on the underside of the mounting flange.
Mounting Flange
The mounting flange filters the fuel before it enters the fuel delivery line and provides the fuel and electrical interfaces between the interior and exterior of the fuel tank. The mounting flange is installed in the top of the fuel tank on the RH (right-hand) side. A gasket, retainer ring, clamp ring and six nuts secure the mounting flange to the top of the fuel tank. The mounting flange aperture provides access to the fuel tank interior.
A connector for the fuel delivery line is located in the top of the mounting flange. Two drain connectors, one for each side of the fuel tank, are located in the mounting flange. Under the RH (right-hand) drain connector is a pipe that extends to the bottom of the tank. Under the LH (left-hand) drain connector is a stub pipe, which connects to a pipe attached to the remote pump housing on the LH (left-hand) side of the fuel tank.
The bowl on the underside of the mounting flange contains a fuel filter element and incorporates the fuel inlet connector. The fuel filter element is non-serviceable and can only be replaced by replacing the mounting flange. Two cables connect an electrical connector to a ground point on the base of the filter bowl.
A six pin electrical connector, located between the drain connectors, provides the electrical connection between the vehicle wiring and the mounting flange ground point, the fuel pump and the fuel level sensors.
Pressure Ventilation Valve
The PVV is installed in the pipe between the pump module and the mounting flange to protect the system from excess pressure. The PVV releases fuel back into the tank if pressure in the pipe increases to 7.3 to 8.3 bar (105.9 to 120.4 lbf/in.2).
Liquid Vapor Separator
The LVS prevents the escape of liquid fuel through to the fuel tank vent pipes. The LVS is installed in a bracket in the top center of the fuel tank. Vent pipes connect the LVS to two connectors in the upper rear corners of the fuel tank. The RH (right-hand) connector is for a vent pipe connected to the top of the fuel filler pipe. The LH (left-hand) connector is for a vent pipe connected to the EVAP (evaporative emission) canister. For additional information, refer to Evaporative Emissions Description and Operation
Three valves are incorporated into the LVS:
- An OPRV, to relieve any excess pressure in the fuel tank into the LVS
- A FLVV, to limit the maximum fuel level when filling the fuel tank
- A ROV, to prevent the escape of fuel through the vent pipes if the vehicle overturns, and allow the fuel tank to vent when the FLVV is closed (i.e. when the fuel tank is full).
Vapor leaving the fuel tank passes through either the FLVV or the ROV during normal vehicle use. During filling, if the fuel reaches the full level the FLVV closes and prevents fuel vapor passing through to the LVS. This causes the pressure in the fuel tank to rise, which in turn causes the pump filling nozzle to cut off at approximately 17 mbar (0.25 lbf/in2).
The ROV contains a valve that closes if the vehicle overturns, and prevents liquid fuel escaping from the fuel tank through the vent pipes.
The ball in the top of the ROV provides a pressure hold function, which is set at 45 mbar (0.65 lbf/in2). This prevents trickle filling or over filling of the fuel tank.
Remote Pump Housing
The remote pump housing is where fuel from the LH (left-hand) side of the fuel tank is drawn from to fill the swirl pot in the pump module. The remote pump housing is installed on the front face of the LH (left-hand) rear baffle. Clips integrated into the remote pump housing hold the LH (left-hand) fuel level sensor and the pipe from the LH (left-hand) drain connector on the mounting flange.
Fuel Level Sensors
Two identical fuel level sensors are installed in the fuel tank. One is mounted on the pump module and one is mounted on the remote pump housing. The fuel level sensors are connected to the BJB (battery junction box) via the connector on the mounting flange.
The fuel level sensors are magnetic passive position sensors. Each sensor consists of a sealed housing that contains 51 film resistors mounted in an arc on a ceramic surface. The film resistors range in value from 51.2 to 992.11 Ohms and 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 a lever and float arm.
The magnet pulls the flexible contacts onto the opposing film resistor contacts, forming an electrical circuit. As the float arm moves, the magnet follows the arc of film resistors and changes the point at which the flexible contacts are pulled onto the opposing film resistor contacts, which changes the resistance in the circuit.
Sensor Operating Principle
Fuel Filler Check Valve
The fuel filler check valve prevents the escape of fuel through the fuel filler pipe if the vehicle overturns. The fuel filler check valve is installed in a stub pipe in the rear right corner of the fuel tank and sealed with an O-ring seal.
A door on the fuel filler check valve is normally held closed by a spring. During filling, the weight of fuel in the fuel filler pipe is sufficient to open the door and allow fuel into the fuel tank.
FUEL PUMP DRIVER MODULE
The FPDM (fuel pump driver module) controls the speed of the fuel pump to match the fuel demand of the engine. The FPDM (fuel pump driver module) is installed in the RH (right-hand) end of the evaporative emission canister.
The pump speed required is calculated by the ECM (engine control module) and transmitted to the FPDM (fuel pump driver module) in a PWM (pulse width modulation) signal.
FUEL FILLER PIPE
The top of the fuel filler pipe is located above the right rear wheel. The filler cap is a conventional screw in type which is secured to the vehicle with a tether. The filler cap is covered by a plastic door, which has a locking motor controlled by the active anti-theft system. For additional information, refer to Anti-Theft - Active
The fuel filler pipe is a stainless steel fabrication which is secured to the vehicle body by two brackets and a flange. A stub pipe is incorporated into the top of the fuel filler pipe for connection of a vent pipe from the fuel tank. A baffle and flapper are installed in the top of the fuel filler pipe. The baffle restricts the diameter of the fuel nozzle that can be used to fill the fuel tank.
The bottom of the fuel filler pipe locates in a flexible hose attached to the fuel filler stub pipe in the rear right corner of the fuel tank. Both ends of the hose are secured with worm drive clamps.
VENT PIPE
The vent pipe connects the vent connector at the right rear corner of the fuel tank to the stub pipe in the head of the fuel filler pipe. Quick release connectors attach the vent pipe to the vent connection and the stub pipe. Cable ties secure the vent pipe to the fuel filler pipe.
FUEL DELIVERY LINE
The fuel delivery line delivers fuel from the mounting flange to the engine compartment. The fuel delivery line is routed along the front of the fuel tank and under the floor of the vehicle on the LH (left-hand) side. Clips secure the fuel delivery line in place on the fuel tank and under the floor. At the front LH (left-hand) corner of the fuel tank a manifold is installed in the fuel delivery line to allow installation of the fuel LP sensor.
FUEL LP SENSOR
The fuel LP sensor supplies a pressure signal to the ECM (engine control module) to enable closed loop control of the fuel pump. The fuel LP sensor is installed in a manifold in the fuel delivery line, at the front left corner of the fuel tank.
CONTROL DIAGRAM
PRINCIPLES OF OPERATION
Fuel Level Sensors
The AJB (auxiliary junction box) sends a separate signal to each of the fuel level sensors. As the float arms of the fuel level sensors move, the resistance across the fuel level sensors changes. Thus the level in the fuel tank determines the value of the signals from the AJB (auxiliary junction box).
From the two signal values the AJB (auxiliary junction box) derives a fuel quantity, which it incorporates into a medium speed CAN (controller area network) message for the instrument cluster. For additional information, refer to Instrument Cluster
In addition to using the fuel quantity signal itself, the instrument cluster also transmits it on the high speed CAN (controller area network) for the electronic engine controls system. For additional information, refer to Electronic Engine Controls Electronic Engine Controls
For additional information, refer to Electronic Engine Controls Electronic Engine Controls
Fuel Pump
The FPDM (fuel pump driver module) is powered by a supply from the fuel pump relay in the AJB (auxiliary junction box). The fuel pump relay is energized on opening the driver's door, pressing the start button only or pressing the start button and the footbrake (which initiates engine cranking). The FPDM (fuel pump driver module) supplies power to the fuel pump, and adjusts the power to control the speed of the fuel pump and thus the pressure and flow in the fuel delivery line.
A PWM (pulse width modulation) signal from the ECM (engine control module) tells the FPDM (fuel pump driver module) the required speed for the fuel pump. The on time of the PWM (pulse width modulation) signal represents half the fuel pump speed, e.g. if the PWM (pulse width modulation) signal has an on time of 50%, the FPDM (fuel pump driver module) drives the pump at 100%.
The FPDM (fuel pump driver module) will only energize the fuel pump if it receives a valid PWM (pulse width modulation) signal, with an on time of between 4% and 50%. To switch the fuel pump off, the ECM (engine control module) transmits a PWM (pulse width modulation) signal with an on time of 75%.
The output pressure from the fuel pump will change with changes of engine demand and fuel temperature. The ECM (engine control module) monitors the input from the fuel LP sensor and adjusts the speed of the fuel pump as necessary to maintain a nominal output pressure of 450 kPa (4.5 bar; 65.3 lbf/in.2), except during engine start-up. At engine start-up the target pressure for the fuel delivery line is 630 kPa (6.3 bar; 91.4 lbf/in.2).
If the SRS (supplemental restraint system) outputs a crash signal on the high speed CAN (controller area network), the ECM (engine control module) de-energizes the fuel pump relay to prevent any further fuel being pumped to the engine.
If the ECM (engine control module) does not detect pressure in the fuel delivery line, it stops, or refuses to start, the engine and stores the appropriate DTC (diagnostic trouble code).
The ECM (engine control module) receives a monitoring signal from the FPDM (fuel pump driver module). Any FPDM (fuel pump driver module)
DTC (diagnostic trouble code) are stored by the ECM (engine control module).
DTC (diagnostic trouble code) can be retrieved from the ECM (engine control module) using the IDS (Integrated Diagnostic System). The FPDM (fuel pump driver module) itself cannot be interrogated by the IDS (Integrated Diagnostic System).