Which causes come into question on a Faber-Castell Classic fountain pen with too strong ink flow and a loose, push-out feed in the section, and are Pelikan cartridges compatible?

Pelikan cartridges generally also fit in Faber-Castell pens and are now and then used without problems. If the feed can be pushed out of the section, the Faber-Castell service is mostly responsible — a simple forceful reinsertion can negatively affect ink flow. If the nib scratches, the cause lies not in the feed but in bent nib tines; that can often be put right locally by a writing-instrument dealer or by sending in to Faber-Castell.