Several inkjet cartridge models made by HP are equipped with an inner ink bag inside their plastic housing. At the bottom of this ink bag there is a black ink pump installed. It is necessary to mak this pump part free from air after refilling to ensure that the cartridge is not messaged as empty by the printer anymore.
HP inkjet cartridges with this design are:
HP 10 - C4841AE, C4842AE, C4843AE, C4844AE
HP 11 - C4811A, C4812A, C4813A
HP 82 - C4911A, C4912A, C4913A
HP 88 - C9385AE, C9386AE, C9387AE, C9388AE
HP 88 XL - C9396AE, C9391AE, C9392AE, C9393AE
The ink bag inside the cartridge models has a frame frame structure. In its bottom there are side by side the ink port, in the middle the ink pimp and the fill port. The fill port is closed in original condition by a rubber ball. Inside the ink pump there is check valve that prevents ink flowing back from the pump section into the ink bag when the printer´s pump stick presses on the ink pump on the cartridge. In orignal condition the ink bag and the ink pump as well are completely filled with HP printer ink.
When printing the HP cartridge to the ink level status empty the black rubber part on the ink pump bulges inwards. As soon the printer´s pump stick has no contact anymore to the ink pump the printer will show this inkjet cartridge as empty. To be able to print with a refilled HP cartridge of this type it is necessary to fill the ink pump with ink again.
For refilling such a HP cartridge we recommend to push the rubber ball closing the fill port into the ink bag. That is less complicated than trying to pull that plug out. Fill the suitable refill in into the ink bag and press the bag together very carefully to press the air out as much as possible. Close the fill port by using a suitable silicon plug or rubber plug.
Position the HP inkjet cartridge on its side - the ink port should be located above the ink pump and the fill port. Use a refill syringe with mounted needle and press the needle into the rubber sealing in the ink port carefully. Pull out the syringe´s plunger. Air, remaining in the ink bag and the ink pump, is pulled out and ink is flowing from the ink bag through the open check valve into the ink pump section. By this the ink pumpe bulges outwards again. Pull out air as long as some ink is extracted from the ink port. The ink pump is filled then with ink again.