low oil pressure gauge reads 0 psi on a custom installation

[lalondem_98]

Edge SE 2010.  Just before the water pump failed there was a moment where the engine sounded like no oil was circulated so when I replaced the water pump and timing chains and also replaced the oil pump (Melling M390, rockauto).  I understand that it is very possible that the oil-not-circulated noise was due to coolant in the oil but at 230000Km and "being there" for repairs it made sense to change it anyways.  When I finished the repairs I wanted to prime the oil pump and crank the engine without having it started by using the fuel shutoff switch however it was too painful to disconnect it and I was eager to start the engine so I forgot about priming, turn the key and it started right away and a huge smile was seen! Here is my first question: is it possible to have air trapped somewhere? either in the pump or the passages? I drove the car around many times so it if could eliminate by itself it is done by now.

 

Nervous about the oil pressure I installed an aftermarket oil pressure gauge (2 in. LED Oil Pressure Gauge)  but I had to do some plumbing with a 1/4 male NPT bar or block with a 1/4 female NPT and a 1/8 female NPT; the ford oil pressure sensor is connected at the end of the bar or block in the 1/4 FNPT, a 9 inches high pressure hose is connected in the 1/8 FNPT and at the end the Titan sensor is connected.  See the 2 pictures.  Remember the smile above? Well there was none this time when I started the car....the oil pressure light in the dash is constantly lit and the gauge reads 0 psi; the engine is running fine but noisier than usual...giving the impression oil is lacking.  I get it that my custom setup is making both sensors to report no pressure.  Anyone ever installed an aftermarket oil gauge?  I also forgot to mention that the initial Ford oil pressure sensor failed and flooded the area around the alternator , and the alternator itself too and the engine stalled... I could not restart it until the next morning once the oil has dripped out.