PIAGGIO 500 cc Service Manual page 160

Fuel injection
Allow the system to purge for a few seconds.
Check that the system has no external leaks.
Check the adjusting pressure with pump feed tension of more than 12 V.
Adjusting pressure = 300 - 320KPa (3 - 3.2 BAR)
NO
YES
The pressure regulator is efficient
Pressure too high
Check that the return duct is not clogged
or compressed.
NO
Replace the pressure regulator
See page 9-54 - pump support
overhaul.
Adjusting pressure too low
Activate pump revolution again. Using long, flat-tonged pliers,
squeeze the return duct for a moment acting only on the extention
part of the special tool.
(the current tube does not allow this operation).
fuel pressure = greater than 300 KPa (3 BAR)
YES NO
9 - 48