I have a weird issue which I cannot seem to figure out. I have a prosports premium oil pressure gauge, the sender is on the "T" for my oil feed line. To test functionality of the gauge, I put compress air on the sender unit and it reads but when I have it on the firewall "T" it reads "0" psi. There is oil traveling through the feed line. so I don't get why it reads 0. does it not build any pressure? thanks in advance.