Have you checked ALL the wires. It sounds as if the wire got disconnected from the oil pressure sending unit on the engine, right behind the distributor. Otherwise I would check the wires to see if they're good. If they are good it sounds like the guage is the problem, or possibly the oil pressure sending unit. How to check them is beyond me, so I would contact Harry Pellow at
www.hcpresearch.com if thats the case. Good luck!
------------------
Joshua Harrison
1968 912 Coupe