PIAGGIO MP3 400 i.e., Service Manual, Page: 199 / 394

- Lambda probe strength
The system implements an idle feeding correction with cold engine through 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 combustion.
In all conditions of use, mixture preparation is managed by modifying the injector opening time.
The fuel supply pressure is kept constant based on the ambient pressure.
The fuel supply 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 a pipe with fast-release fittings. The pressure regulator is located at the
beginning of the circuit.
The fuel pump is controlled by the MIU control unit ; this ensures the scooter safety
The ignition circuit consists of:
- HV coil
- HV 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 rev counter signal is missing, or when the failure involves the
control circuits:
- Fuel pump
- HV coil
- Injector
MP3 400 i.e.
Injection
INJEC - 3