Is there a method to test a pump that uses packing for a seal when on the bench and no motor attahed? This is so the pump is not installed and then find out that it is leaking way to much when operated.
Sorry, have never seen the need for such a test. If a pump with new packing leaked "way too much" when run, then it would probably take less time to check why it was and then repack, if the installed packing could not be taken up a bit more.
There is very little to go wrong with packing - insufficient compression, over compressed packing or wrong size packing ? Remember it must leak to work properly to lubricate...
Remove current packing and repack with proper packing leave gland out to full for further tightening under pressure. There is no need to test as long as you use the proper packing. Contact a packing manufacturer/supplier and read up on packing for oil/water/steam packing at pressures you need.