VESPA 633844 IT, Service Manual

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b. Wrong idle mixture
c.Incorrect reset of the throttle valve position sensor
2 MIU system faults may be caused by loose connectors. Make sure that all connections have been
correctly made.
Check the connections as follows:
A check that the terminals are not bent.
B check that the connectors have been properly connected.
C see whether the malfunction can be fixed by shaking the connector slightly.
3 Check the entire system before replacing the MIUIf the fault is fixed by replacing the MIU control unit,
install the original control unit again and check if the fault occurs again.
4 When troubleshooting use a multimeter with an internal resistance over 10 Ohm /V. Instruments that
are not suitable might damage the MIU control unit. Instruments must be used with definitions over 0.1V
and 0.5 W , the precision must be greater than 2%.
1. Before fixing any part of the injection system, check to see if there are any registered faults. Do not
disconnect the battery before checking for faults.
2. The fuel feed system is pressurised at 250 kPa (2.5 BAR). Before disconnecting the quick coupler
of a pipe in the fuel supply system, check that there are no naked flames, and do not smoke. Act with
caution to prevent spraying in the eyes.
3. When fixing electric components, operate with battery connected only when actually required.
4. When functional checks are performed, check that the battery voltage is more than 12V.
5. Before trying to start up, check to make sure there is at least two litres of fuel in the tank. Failure to
respect this norm will damage the fuel pump.
6. If the scooter is expected to remain unused for a long time, refill the tank up to a little over half the
level. This will ensure the pump will be covered by fuel.
7. When washing the vehicle, be careful with the electric components and wiring.
8. When an ignition fault is detected, start the checks from the battery and the injection system con-
nections.
9. Before disconnecting the MIU control unit connector, perform the following steps in the order shown:
- Set the switch to «OFF»
- Disconnect the battery
Failure to respect this norm may damage the control unit.
10. Do not invert the polarity when fitting the battery.
11. To avoid damage, only disconnect and reconnect the MIU system connectors if required. Before
reconnecting, check that the connectors are dry.
12. When carrying out electric inspections, do not force the tester probes into the connectors. Do not
take measurements not specifically foreseen by the manual.
Vespa GTV 250 i.e.
Injection
INJEC - 5