Got a VW polo 2002-2005 model, 1.2 petrol engine, chain driven oil pump and the car has covered 70k miles. Was driving along and the oil pressure warning light came on, along with quite a large loss of power having to rev it more than usual.

So far, I've done the obvious things; changed the oil and filter and changed the oil pressure switch which made no difference and didn't put out the light. In fact I had left the car for a day after I carried out the changes and the car stalled twice which was quite unusual. Trying to find the problem I removed the sump, the oil in there had no sign of any bearing wear (I was told little bits of metal would be present in the sump if this happened) and removed the oil pump. Inspected and took apart the pump, cleaned all the parts including the pick up, strainer and pressure relief valve and all looked ok so fitted the pump back on. I've also had a breif check of the timing chain appears to be fine and not damaged. Managed to borrow a friends oil pressure gauge and tried that out and now it hasn't got any pressure at all. The engine still ticks over and idles but I don't want to rev it so I don't cause any other damage. I am thinking about buying a new oil pump and fitting that to see if that cures the problem but they are £180 to buy as you can only get them from VW so want to try to avoid that if I can.

I'm a trainee mechanic and inexperienced but attempting to rectify the problem myself to save the labour costs of taking it to a garage so any help would be appreicated. Thanks