VESPA GTV 250 i.e. 2008 Service Station Manual page 155

Vespa GTV 250 i.e.
Injection
MIU injection system
This vehicle is fitted with an integrated injection and ignition system.
Injection is indirect in the manifold through an electro-injector.
The injection and ignition are timed on the four-stroke cycle by means of a tone wheel keyed on to the
crankshaft (24-2 teeth) and pick-up sensor.
Mixture and ignition are managed on the basis of engine revs and throttle valve opening. Further cor-
rections are made according to the following parameters:
- Coolant temperature
- Intake air temperature
- Lambda probe
The system implements cold engine idle fuel/air mixture correction with a stepper motor on a by-pass
circuit of the throttle valve. The control unit manages the Stepper motor and the injector opening time,
thereby ensuring the idle steadiness and the proper mixture.
In all conditions of use, mixture preparation is managed by modifying the injector opening time.
The fuel system pressure is kept constant in relation to ambient pressure.
The fuel system circuit consists of:
- Fuel pump
- Fuel filter
- Injector
- Pressure regulator
The pump, the filter and the regulator are placed inside the fuel tank on a single support.
The injector is connected by two pipes provided with fast-release fittings. This results in a continuous
circulation, thereby avoiding the risk of fuel boiling. The pressure regulator is at the end of the circuit.
The fuel pump is controlled by the MIU control unit; this ensures safety of the vehicle.
The ignition circuit consists of:
- H.V. coil
- H.V. cable.
- Shielded cap
- MIU control unit
- Spark plug
The MIU control unit manages ignition with the best advance ensuring four-stroke timing (ignition only
in the compression phase) at the same time.
The MIU injection-ignition system controls engine functions by means of a pre-set program.
Should any input signals fail, an acceptable working order of the engine is ensured to allow the user to
reach a service station.
Of course, this cannot happen when the rpm-timing signal is missing, or when the failure involves the
control circuits:
- Fuel pump
INJEC - 155