This plunger-less injector is one that will be injected into cartridge. Don't put any ink in plunger-less injector yet, just inject it into cartridge. Use a 4" needle and get it in as far as you can. The middle chamber in C1823 / C6625 / C6578 / HP51641 cartridges will not go as deep. Don't force it.

Now get your other injector, one that still has plunger. Using this injector measure out proper amount of ink and slowly shoot it into plunger-less injector's cavity.

The ink will seem like it's not going anywhere at first but let it sit this way for about 20 minutes. It will slowly go into cartridge. Depending on your elevation and amount of ink it may take less than 20 minutes.

Repeat this procedure with other colors.

That's all there is to it. A little patients goes a long way.

While we're on subject I want to point out that cross contamination is not always caused by overfilling. Another effect called "nozzle migration" can also contaminate colors. Nozzle migration occurs when print head comes in contact with a non absorbing surface such as a plastic baggie or print head tape improperly applied. Or even a kitchen table.

The inks can migrate across print head by capillary action contaminating other color chambers. Before applying print head tape it is ESSENTIAL that print head is completely dry of any ink build up. Also do NOT store color cartridges in a plastic bag without some protection to print head. The best protection is a cartridge clip.

I learned this hard way. One time I had a load of virgin HP color cartridges that I sent off remanufacturer. I got whole shipment back because I tediously wrapped each one in plastic bags without anything protecting print heads. Every one had nozzle migration and they rejected them all. What a waste!

Actually effects of nozzle migration may go away by itself by using cartridge, If it's not too bad, that is. Printing out a color test pattern a few times can help a lot.