Warning: The following procedure will merely relieve the pressure in the fuel system -remember that fuel will still be present in the system components and take precautions accordingly before disconnecting any of them.
1 The fuel system of Fiat Punto is defined as the tank-mounted fuel pump, the fuel rail the fuel injectors, and the metal pipes and flexible hoses of the fuel lines between these components. All these contain fuel which will be under pressure while the engine is running and/or while the ignition is switches on. The pressure will remain for some time after the ignition has been switched off, and must be relieved before any of these components are disturbed for servicing work.
2 Disconnect the battery negative terminal.
3 Remove the air cleaner assembly.
4 Locate the Schrader valve situated at the right-hand end of the fuel rail (see illustrations). The Schrader valve works like a tyre valve whereby on depressing the central plunger, the Fiat Punto system fuel pressure will be released.

Fuel system depressurization Schrader valve location (arrowed) on SOHC (8-valve) engines ...

... and on DOHC (16-vaive) engines

5 Withdraw the protective plastic cap from the top of the valve (see illustration)

Withdraw the plastic cap from the top of the Schrader valve ...

6 Place an absorbent rag around the valve using a small screwdriver, slowly depress the central plunger to allow the pressure to be released (see illustration). Ensure that the rag completely covers the valve to catch the fuel spray which will be expelled.

... then depress the central plunger to allow the fuel pressure to be released

7 On completion of the operations for which system depressurisation was necessary, refit the Schrader valve cap and reconnect the battery negative terminal. Refit the air cleaner assembly of Fiat Punto.