If it has been run like that over a period of a year or more it may likely need new bearings, so they need checking out.
The pump on the 60 engine is a vane pump and is more prone to failure than the gear pumps on the 70, 80 and 90. Not sure how much they can be serviced - probably very little as the service book says replace entire pump if worn. They are more difficult to prime as well but pumping oil into the sump via the gallery is usually a good bet.
As an aside, the only engine oil pumps that I have experienced which have comprehensively failed have been vane types.
If only three vanes, one sticking would mean no oil flow at all. Failed pumps usually exhibit signs which are easy to spot.
It would appear that the pump has not been checked? Check also for any leak into the pick-up and the operation of that non-adjustable pressure relief valve.