Aprilia Consumer Service Spa
Technical Service and Training
Release 4 july 99
This material is didactic and
may be changed following the technical
development of the product
3.2 FUEL CIRCUIT
The fuel circuit is made up of the following components:
1 fuel pump
2 fuel feed pipe
3 pressure regulator
4 injector.
The fuel pump is immersed in the fuel tank and pumps the pressurised fuel to the feed pipe, where
the pressure regulator keeps the fuel pressure about 3 bars higher than the intake pressure. The
excess pressure is “vented” by the regulator and the excess fuel goes back to the tank through the
return hose. The regulator is controlled by the inlet manifold average pressure. The pressure on the
injector is thus compensated by the intake ducts pressure.
The fuel pump is the WESCO type. The functions of the pump are as follows:
1. Pressurise the fuel in the fuel feed circuit
2. Relief valve for p> 5-6 atm
3. Check valve to maintain the pressure in the circuit when the engine is turned off
There is a mesh filter at the pump inlet port; after filtering, the fuel is sent to the impeller-type pump
chamber (see fig.).
The fuel pump capacity is about 60 litres/h.
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