Rebuilt engine with sensor problems?

[xgrove]

1991 BMW 318i - E30 - M42 Engine

We received a 1991 318i that had a fully rebuilt but unstarted motor. We worked through a number of problems and got the motor running. We have two problems right now that are puzzling us:

(1) Oil pressure light goes on after 2-3 minutes (even though we replaced the oil sensor and have measured adequate oil pressure via a physical gauge hooked up to the sensor port).

(2) Temperature light goes on immediately (thermostat is new but I'm not sure if the temperature sensor has been replaced).

I'm looking for ideas and would be REALLY appreciative.

- Richard