184000264 - INTRODUCTION - FUEL TANK AND PIPES
CONSTRUCTION FEATURES
The fuel supply system is divided into a low pressure circuit and a high pressure circuit.The low pressure circuit consists of:
- – immersed auxiliary electric pump;
- fuel filter;
- return manifold.
The high pressure circuit consists of:
- pressure pump;
- distribution manifold.
OPERATION
The fuel is drawn from the tank by means of a pre-supply electric pump operating at 12 V, which provides a sufficient flow rate to ensure the lubrication and cooling of the pressure pump as well.The diesel filter is mounted between the electric pump and pressure pump.The high-pressure hydraulic connections are made by means of steel pipes with an internal diameter of 2 mm and external diameter of 6 mm.The pump recirculation must be sent to the tank separately from the fuel injector recirculation which, after being collected in a single pipe, is also sent to the tank.
FUEL TANK
Construction features
The fuel tank, with a capacity of about 49 litres, is made of a plastic material.It is fitted with a flexible filler and comprises the seating for fitting the fuel pump and fuel gauge sender unit.
LOW PRESSURE ELECTRIC FUEL PUMP
Construction features
The electric pump immersed in the fuel is the positive-displacement roller type with a permanent-magnet brush motor.
Operation
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.SAFETY AND VENTILATION VALVE
Operation
This valve is built into the fuel filler cap, and it carries out the following functions, depending on the pressure present in the tank:
- it discharges to the outside any surplus pressure which is created inside the tank (safety function); the pressure acts on the plate (2) and, overcoming the load of the spring (1), allows the surplus vapours to be discharged to the outside;
- it allows external air to flow into the tank when an excessive vacuum is created in the tank, following the consumption of fuel (ventilation function). In this case, when the vacuum exceeds the load of the spring (4), it moves the valve (3), allowing air to enter.
