Vespa Primavera 50 - Service manual > Injection

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.

Combustion and ignition are managed on the basis of engine revs and throttle valve opening. Further corrections are made according to the following parameters:

• Engine temperature
• Intake air temperature
• Lambda probe

The system implements cold engine idle fuel/air mixture correction with an adjustment device on a bypass 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 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 a pipe with fast-release fittings. The pressure regulator is located at the beginning of the circuit.

The petrol pump is controlled by the injection control unit; this ensures safety of the vehicle.

The ignition circuit consists of:

• H.V. coil
• H.V. cable.
• Shielded cap
• Injection ECU
• Spark plug

The injection control unit manages ignition with the best advance ensuring four-stroke timing (ignition only in the compression phase) at the same time.

The injection/ignition system manages the engine function according to 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
• H.V. coil
• Injector

The control unit is fitted with a self-diagnosis system connected to a warning light on the instrument panel.

Failures are detected and restored by the diagnostic tester.

In any case, when the fault is no longer present, data storage is automatically wiped clean after 16 cycles of use (cold starting, running at regular engine temperature, stop).

The diagnostic tester is also required for adjusting idle speed carburetion.

Specific tooling

020922Y Diagnosis Tool

The injection control unit has a decoder for the anti- theft immobilizer system.

The injection control unit is connected to a diagnostic LED on the instrument panel that also carries out the deterrent flashing functions.

• Precautions
• Fuel supply system

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