UK Car Repair: Low oil pressure, oil pressure sender, low oil pressure

Question
Hi, I own a 1993 Jaguar XJ6 that has a problem with the oil pressure dropping when the engine warms up. The RPMs seem to be where they should but the pressure still drops to "0" when the engine is warm and the car is in gear at a stop. Once the accelerator is pressed to presume travel the pressure rises. Can you help me figure out what the problem is? Sensor? or Pump?

Answer
The oil pressure sender units on these cars were quite unreliable. If I had the problem I would remove the unit (left side of block below the inlet manifold, closer to the front) and put a gauge into the block and check the actual reading. You probably don't have access to the tools to do this so, buy a new unit from any of the aftermarket suppliers,and fit it.