another reason the pressure may not show an increase: leaking orings on the coupler!
i traded an item for these couplers which were quite old. cleaned them up, lubed the orings (which looked fine), and put them to work. Well, the orings were apparently too compressed to hold a perfect seal. leaked just enough to show a little pressure on the gauge, but not hold it over 2 or 3 psig. should get some good feedback now.