3308463 - 1040A fuel tank and components (Automatic transmission)

SUBMERGED PUMP ASSEMBLY COMPLETE WITH FUEL GAUGE SENDER UNIT

The fuel pump forms a single assembly with the fuel gauge sender unit and fuel filter; the components cannot be replaced individually.On EURO 3 versions, an O-ring ensures a seal between the pump cover and fuel tank. Submerged fuel pump assemblies with level gauge control are not interchangeable between previous versions and the EURO 3 version.

Electric fuel pump

The electric pump immersed in the fuel is the positive-displacement roller type with a permanent-magnet brush motor.The impeller (1) rotates, driven by the motor, creating volumes (2) which move from the inlet port (3) to the supply port (4).These volumes are defined by rollers (5) which, whilst the motor is rotating, adhere to the outer ring (6).The pump has two valves, one single-acting valve to prevent the fuel circuit from being drained (with the pump not working) and a second excess pressure valve (7) which recirculates the supply when the pressure exceeds 5 bar.

MULTI-PURPOSE VALVE

The multi-purpose valve has the following functions:

  • pressurization of the tank
  • retention
  • the seal in the event of roll-over
The multi-function valve is thermowelded and so cannot be replaced individually.

Pressurizing the tank

The tank pressure is kept at between 55 - 75 mbar by means of a fluoro-silicone rubber valve resting on a sealing edge.The valve is supported by a stainless steel plate and counteracted by a spring.When the pressure in the tank exceeds the specified value, it overcomes the resistance of the spring and the valve is able to rise, allowing vapours to flow to the canister.When the pressure returns to the correct limits, the valve closes again.

Retention

Under particular driving conditions, a vacuum could be created in the tank because of:

  • temperature changes
  • fuel consumption.
In this case, the valve's function is to restore the pressure of the tank by allowing air in.A fault in this function could cause the engine to miss or stall, because of difficulties in supplying the fuel pump.This function is carried out by the 'goose beak' valve formed directly out of the fluorosilicone rubber.

Seal in the event of roll-over

The roll-over function prevents fuel from leaking from the tank if the vehicle overturns or is on a very steep slope.During normal driving of the vehicle (bends, acceleration, braking, etc.), the fuel is shaken up and may spill into the canister.The car's high roll-over sensitivity prevents this spillage.The roll-over closure angle is less than 33°.

INERTIA SWITCH

In the case of an impact, the inertia switch, fitted under the driver's seat, interrupts the connection to earth for the electric fuel pump and consequently the supply to the injection system.
A steel ball (1) mounted in a conical housing (2) is normally locked by the attraction force of an adjacent magnet.Under specific acceleration loads, the ball is released from the magnetic lock and gradually emerges from the conical housing in an upward movement, following the angle of the cone.Above the ball, there is a quick-trip mechanism (3) which forms the normally closed (N.C.) electric circuit.When the mechanism is struck by the ball, it changes position from an N.C. circuit to a normally open (N.A.) circuit, breaking the fuel pump's earth circuit.The switch can be reset by pressing a button protected by a soft cover (4).
Even after an apparently minor impact, if there is a smell of fuel or leaks are noticed from the fuel system, do not turn the switch back on, but search for the cause of the problem and remedy it to prevent the risk of fire.Otherwise, if there are no leaks and the vehicle can be restarted, press the button to reactivate the pump.