The liquid filled fuel pressure gauges (such as my Russell pictured below) are notoriously unreliable when mounted on the engine. The pressure change inside the gauge, because of temperature fluctuations, will give you inaccurate readings. The first time you experience this it will throw you for a loop, but the FordFE Forum is replete with liquid-filled gauge stories and, once you get used to it, it's not so bad ... and best of all it still looks nice.
Seriously though, after a while you can kind of figure out why it's reading what it's reading and now you'll know why your engine seems to be running just fine with no fuel pressure whatsoever!
