I had a simiilar problem with my 1.6 cvh. Oil pressure switch was working fine. I took the sump off injected oil straight into the pump.
No matter how long I cranked it for it would not turn the oil pressure light off. I looked on one of the ford forums and apparently it is a common thing on the 1.6 cvh.
In the end I just started it and it went out within a few seconds.