Depends on where it was/is leaking from..
If it was leaking from the pump housing and the barrel, it’s either the orings or the housing is eroded..
If it was leaking at the dv holder, u have to have a special socket to get it loose.. it takes an oring and dv gasket..
If u can get a close up of the housing where the oring rides, I might be able to tell if it’s eroded..??