PIAGGIO 500 cc, Service Manual

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Fuel injection
9 - 3
9
INTRODUCTION
EMS fuel injection system
The fuel injection system used is of the integrated fuel injection and ignition type.
Fuel is injected indirectly into the manifold by means of the electroinjector.
Fuel injection and ignition are timed on a 4-stroke cycle via a phonic wheel splined to the cam shaft control and a
reluctance variance sensor.
Carburation and ignition are managed in relation to the engine revolutions and the opening of the throttle valve.
Further corrections are carried out on the basis of the following parameters:
- Coolant temperature
- Air intake temperature
- Ambient pressure
The system carries out the idling supply correction on a cold engine via a stepper motor inserted on to a by-pass
circuit of the throttle valve. The control unit manages the stepper motor and the timing of the injector opening, thus
guaranteeing idling stability and correct carburation.
Under all working conditions, carburation is managed by modifying the injector opening time.
Fuel supply pressure is kept constant on the basis of ambient pressure.
The feed circuit is composed of:
- Fuel pump
- Fuel filter
- Injector
- Pressure regulator
The pump, filter and regulator are inserted into the fuel tank via a single support.
The injector is connected by means of two quick-connection tubes. This allows continuous circulation and avoids
the risk of petrol overheating. The pressure regulator is situated at the end of the circuit. The fuel pump is
commanded by the EMS control unit; thus guaranteeing vehicle safety.
The ignition circuit is composed of:
- H.V. coil
- H.V. cable
- Shielded cap
- EMS control unit
- Spark plug
The EMS control unit manages ignition with optimum advance, at the same time guaranteeing 4-stroke cycle timing
(ignition only during compression stage).
The EMS igntion-injection system manages the working of the engine by means of a preset programme.
Should certain entry signals fail, an acceptable working of the engine is still guaranteed in order that the user may
reach a repairs centre.
Obviously, this will not happen if the revolutions signal fails, nor if there is an anomaly in the control circuit:
- Fuel pump
- A.T.Coil
- Injector