Attention! We work on a cold engine.
The pressure in the fuel rail is checked with a conventional pressure gauge (e.g. from a tire pump).
We put an oil and petrol resistant hose on the threaded fitting of the pressure gauge (with inner diameter 12 mm) and secure it with a clamp.
Unscrew the protective cap on the rear end of the fuel rail.
Using the wheel valve cap, unscrew the spool from the fuel rail fitting (for clarity, the operation is shown on the removed ramp)...
... and, gradually releasing the fuel pressure, we take out the spool.
We put the pressure gauge hose on the ramp fitting and fix it with a clamp.
We start the engine and when it is idling...
... check the fuel pressure, which should be 2.8–3.2 bar (2.8–3.2 atm).
Remove the vacuum hose from the fuel pressure regulator.
With a working regulator, the fuel pressure should increase by 0.2–0.7 bar (0.2–0.7 atm).