Manual says :

WARNING: THE FUEL SYSTEM IS UNDER A CONSTANT PRESSURE
(EVEN WITH THE ENGINE OFF). BEFORE TESTING OR SERVICING
ANY FUEL SYSTEM HOSE, FITTING OR LINE, THE FUEL SYSTEM
PRESSURE MUST BE RELEASED.
Turn the ignition off.
Install a fuel pressure gauge.
Turn the ignition on.
With the DRB IIIT, actuate the Fuel Pump Relay and observe the fuel
pressure gauge.
Note: Fuel pressure specification is 3.7 to 4.2 bar (54 to 61 psi).