Fuel pressure

Hi All I am testing my 1986 DX fuel system. Pressure gauge in the line to the control pressure regulator. With open line a cold start reads 1.4 goes to 3.6 over time (- correct). But if I close the line I only get just 1 bar. With the line closed reading must be at least 5 bar.
I did test the injectors (all a Little more then specifications). Filter, in tank pump, pump, injectors fuel lines all new. Tank clean (100% clean? it’s from 86).  How can I get fairly correct output from injectors, reading 3.6 with valve open, but only 1 with the valve closed? Am I doing anything wrong or is it magic? Suggesting most appreciated....

Which side of the shut off valve is the gauge ?, gauge needs to be metering head side of the valve  

Thank you!

I already realized it….

Joergen