Is this a new problem or did you just replace the oil sending unit and by chance the wire harness. I would think the oil pressure with the key on and harness plugged in should read O psi. and if you disconnect the harness with power on the gauge will max out, when you plug the harness back in to the sending unit it should read 0 again.
If you start the car and the pressure still reads 0, then ....it is a bad sending unit....or the oil passage is clogged in the block or oil sending unit...or....you have 0 oil pressure.
This is the unit you have, correct? http://www.fierostore.com/P...px?s=51402&d=172&p=1
In the Great Northwest!
[This message has been edited by NW-Fiero (edited 04-28-2014).]