I own a HP 3420 model Inkjet printer. For refilling its cartridge I purchased an Amkette black e-fill Inkjet refill system. However the HP cartridge (HP 27) doesn't fit into the refill clip of amkette. Hence I refilled the cartridge by injecting ink into the vent below the sticker with an injection syringe. With that ink oozes out of the print head. Moreover level of ink is also not shown to have increased when "Ink level" is seen on monitor. Is my refilling process wrong? Plz advice how to refill.