Oil Pump

I own a Porsche 944 1986 2.5 Lux and have just suddenly lost all oil pressure. The car has always taken a while to build pressure when first started but held 4-5 bar when driving. The pressure fell all of a sudden and so I think it is the oil pump that has failed. Does anybody have any ideas if I might be right or if they can think of any other reason for this fault. I would also like to know if it is possible to replace the oil pump without removing the engine, and if you have any tips for doing it.

Cheers

Tom

Oil Pickup, leak, pump, etc

Use a mechanocal guage first t be sure that the sender did not fail. I 've seen that happen before

Use a mechanocal guage first t be sure that the sender did not fail. I 've seen that happen before
Sender has not failed, no oil getting to tappets, does the engine have to come out to replace the oil pump? And where do I find the oil pressure regulator?