oil pressure

[redSRpilot]

earlier today i took off my fuel rail to see if my injectors were leaking, they weren't so i put it all back together. then i went and started my car and my oil pressure gauge now reads 0psi. it was working fine before reading 12psi at idle after it was hot, about 40psi in cruise, and 80psi full throttle. do these sound normal? also, do oil pumps work fine and then just fail with no signs? or is there anything else it could be? im checking my gauge sensor right now, but if its not that im not sure where to go from their.