Ford techs use their system to read it by software.
Electrical won't mimic the O2 not switching unless the O2 itself is bad. Weak ignition will not burn all O2, PCM responds by going too rich trying to correct and it becomes obvious.
On STANDARD zetec there is a spot on driver end of fuel rail that is where the fuel pressure fitting used to be or still is on Euro models. A plate with two bolts in it, when loosened feels like a rubber plug or o-ring in there. I didn't completely remove mine but wondering if it can be pulled and say a 1/8" pipe tap run in there to provide for a fitting of some sort to directly read it. Ain't got that far yet but someday..........
Pump priming up is no evidence of pressure at all.................PCM just runs it for 2 seconds and stops, it is not shutoff by a pressure reading.