When I installed my ZZ4 motor in my 76 I noticed the oil pressure gage quit working so replaced the oil pressure sensor thinking it was bad. The gage in the center console is still is not working. Is there a fuse for the center gages that might have blown? My tempature gage is working.

My oil gage (on the 81) has a little plastic pipe in the back of the gage.  Has a seprate bulb to make the gage visible.

Take the sending unit wire off the unit, and ground it to something close by. With the key On, the gauge should peg out on the high side. If it does not, there is a problem in the wire from the sender unit to the gauge. If you have not messed with the gauge cluster, and only replaced the engine, my guess is the wire got damaged somehow.
There is only one fuse for the gauges, and it is marked as such. It's possible the gauge has failed, too, but I would lean towards a problem in the wiring under the hood.
htht
Adams' Apple2010-05-05 05:12:16

Thanks Joel! I removed the wire connection on the sensor and with the key on the gage pegs at 90 PSI. So the wiring must be ok from what you indicated. I will check the fuse once my son is around as I can't read the print on the fuse box with my old eyes.

If the gauge pegged, the fuse is ok. You either have another bad sensor, or....horrors...no oil pressure!
The gauge has power with the key on, and the sensor provides the ground. Did you ground the sensor wire, or just dis-connect it?

I have been driving the car like this for 500 miles so I have oil pressure, I just don't know how much ....and no I did not ground the sensor wire I just disconnected it. How do I ground it?

Just stick the metal part of the terminal up against the engine, or a bolt somewhere close. See what the gauge does like that. It really sounds like the sensor is the problem. WHere on the block is the sensor located? It's possible that there is no oil pressure at the fitting location, for some reason. It wouldn't be the first time that a block has not be properly drilled.

The terminal is a female boot on the end of the wire that connects to the spade (male) end on the sensor. Should I slip a piece of wire in the boot end and then toutch the other end to the engine block for a ground?
As far as the sensor fitting port location on the block....it's located on the driver's side of the block just aft of the last spark plug. When I removed the old brass fitting that the sensor attaches to the threads were deformed to a larger thread size. Could there be another port that I just didn't notice? The motor is a GM Create ZZ4 block from engine depot in 2009 if that make any difference. 

The fitting should be right there where you say. It should be just above the oil filter. There might also be another one just to the pass side of the distributor, coming out of the top of the block back there. It's hard to get to up there, tho. Earlier small blocks also had another oil pressure tap at the front of the block. just above the water pump, but your's prolly doesn't have that....ya never know.
Yeah, just grab a short piece of wire and stick it into the connector, and ground that bugger somewhere.
You  may want to remove the sensor, and then dis-connect the ignition power tot he distributor, and crank the engine for a couple of seconds, and see if any oil comes out of the hole. It would be best to install a mechanical gauge there temporarily for this test, but if ya don't have one, taking the sender out and cranking it will squirt oil out, if the fitting is open as it should be. Just an idea, but make sure you disable the ignition first...you don't want to start it, just spin it over for 3-4 seconds.

with the sensor removed check the fittings the hole on the sender is real small. After checking the wire like joel said,  you could hook the sender up while it is out, grnd the case and apply a little air to sender then see what the guage reads. If you have an ohmeter i checked an old one I had it read 10 to 20 ohms static and whent up from their as air was applied. Here is a site that helps http://www.europeancorvette.com/html/console_gauges.htmrraider12010-05-07 07:43:50