1. Prepare the vehicle for operations (see "Preparing a car for maintenance and repair").
2. To check the fuel pressure, unscrew the protective cap of the fitting installed on the fuel rail.
3. Put the pressure gauge hose with a special tip on the fitting.
4. Start the engine and check the fuel pressure when the engine is idling. The pressure should be within 2.8-3.2 bar (280-320 kPa).
5. Disconnect the vacuum hose from the pressure regulator and visually assess the pressure change. If the regulator is in good working order, the pressure should increase by 0.2-0.7 bar (20-70 kPa). Otherwise, the fuel pressure regulator must be replaced (see below "Pressure regulator - removal and installation").
The article is taken from an online resource: VazBook.ru