Is it possible that the internals, bearings etc. are so worn that the pressure is not gonna be there with a new pump?
Usualy you would need a lot of miles...no idea ewhatyour motor has.
I have a spare motor in the shop that is locked up...I can pull the pump and ship to you if you want to pay a little for it...you could use it just to test and see if it does the same thing to see if it is the bearings...
Let me know.
Lord send your Holy Ghost into our hearts and make the desire of our hearts Your Will.
Pro-choice, that's a LIE, babies don't choose to die!!