Fuel Delivery System Description and Operation
Fuel Delivery System Description and Operation
General
The fuel delivery system consists of a fuel tank containing an electric fuel pump to supply fuel at a constant pressure to the engine fuel rail. A pipe, routed along the underside of the vehicle, connects the fuel pump to the fuel rail.
Fuel Tank
Fuel Tank And Fuel Pump (NAS):
The fuel tank is located on the underside of the vehicle, forward of the rear suspension subframe. The tank is constructed from moulded plastic and is retained by a tubular cradle which is secured to the vehicle floorpan with four bolts. A heat shield is installed on the LH side of the support cradle to protect the tank from heat radiated by the exhaust system. A fire shield is installed on the RH side of the support cradle.
The fuel tank has a nominal capacity of 60 liters (15.85 US gallons). An aperture in the top surface of the tank allows for the fitment of the fuel pump.
The top of the fuel tank filler tube is located in the RH rear wing panel and is closed by a lockable filler cap. The bottom of the filler tube is connected to the tank by a flexible tube secured with clamps. On NAS vehicles, a flap valve in the fuel tank, at the connection point with the filler tube, prevents vapor from escaping once refuelling is completed and also prevents fuel from escaping if the filler cap or filler tube are damaged in an accident.
On all except NAS vehicles, a vent pipe between the tank and the neck of the filler tube allows air to escape from the tank during refuelling. With the fuel filler cap installed, the tank is ventilated to atmosphere through vent pipes that connect three roll over valves in the tank to the Evaporative emissions (EVAP) system.
On NAS vehicles, during refuelling and with the fuel filler cap installed, the tank is ventilated to atmosphere through vent pipes that connect an Onboard Refuelling vapor Recovery (ORVR) valve and the three roll over valves in the tank to the Evaporative emissions (EVAP) system.
The location of the vent pipe connections on the fuel tank ensures an air space remains in the tank after filling, to allow for heat expansion of the fuel.
The ORVR valve and roll over valves are float valves that prevent fuel from entering the EVAP system vent pipes due to fuel slosh or if the vehicle overturns.
Fuel Pump
Fuel Tank And Fuel Pump (NAS):
The fuel pump is a submersible electric pump located in the top face of the fuel tank. A notched locking ring retains the fuel pump in the tank and requires a special tool for removal and installation. An access panel below the rear passenger seats provides access to the fuel pump for maintenance. The top face of the fuel pump has an electrical connector with power and ground connections to the pump and the fuel gauge rotary potentiometer. A quick fit coupling provides attachment for the fuel feed pipe. A non return valve in the pump outlet prevents fuel draining from the feed pipe back into the tank when the pump is stopped.
The fuel pump is housed in a plastic body which incorporates a coarse mesh filter and a serviceable fine mesh filter. The bottom part of the body forms a swirl pot which maintains a constant fuel level at the pump pick-up. A pressure regulator in the pump body ensures that the fuel rail and the injectors are supplied with fuel at a constant pressure of 3.5 bar (51 lbf/in square). The regulator relieves excess fuel from the pump outlet back to the swirl pot.
Fuel Rail
Fuel Rail And Injectors (NAS):
Three fuel injectors are installed in each inlet manifold and connected to the fuel rail. The injectors are sealed in the fuel rail and the inlet manifolds by 'O' ring seals. A quick release coupling connects the feed pipe from the fuel tank to the fuel rail.
An accumulator is attached to the fuel rail, to damp out pressure pulses from the pump and ensure that the pressure in the fuel rail is constant. On all except NAS vehicles, a vacuum pipe connects the accumulator to the inlet manifold to aid the damping process.
A Schraeder valve is installed in the 'fuel return' pipe (on all except NAS vehicles) or above the accumulator (on NAS vehicles) to provide a pressure test connection for maintenance.
Operation
The fuel pump is controlled by the Engine Control Module (ECM), which switches the fuel pump relay in the engine compartment fuse box to control the power feed to the pump. The electrical circuit for the fuel pump incorporates an inertia fuel cut-off switch attached to the LH front suspension turret. In a collision above a preset deceleration speed, the switch breaks the circuit to the fuel pump to stop the delivery of fuel to the engine. The switch is reset by pressing the rubber top.
WARNING: Ensure there are no fuel leaks and confirm the integrity of the fuel system before resetting the fuel shut-off switch.
The fuel pump outputs more fuel than the maximum load requirement of the engine, in order to maintain a constant pressure in the fuel rail under all running conditions.