[tbirdtbird]

An A is a non-pressurized system. The pump output is delivered to a wide open pipe inside the valve chamber, so there is no way for any pressure to develop. It is a gravity feed system. You would be better off with a gravity gauge. No gravity=no oil flow

Take the gauge off, it serves no purpose. You may as well have installed a geiger counter; it can also try to measure something that is not there.