Ok, enough with chemistry lesson. What I'm saying is even though ammonia is great for dissolving ink please be careful when using it.

Most of toughest clogs can be fixed by soaking print head in a bowl of a 50/50% solution of ammonia and water overnight. If that doesn't work you can soak it in pure ammonia for up to 1 hour then a 100% water rinse.

If your print head is not removable you can inject a diluted ammonia mix (10% ammonia and 90% de-ionized water, or just use Windex) into an empty cartridge and run print head cleanings to get solution into print head. If clog does not open leave printer sit overnight and try it again next day. Many times clog will release overnight as ammonia solution goes to work.

Some people will tell you to use alcohol to unclog cartridges and print heads. While it may work for a short while alcohol will actually increase chances of another clog. This is because alcohol will tend to dry out plastics and metals in head. Alcohol will only fix very mild clogs that could probably be fixed with an aggressive print head cleaning. If you want to do job right use ammonia solutions as I discussed above.

Take injector without plunger and insert it into chamber of cartridge that you are refilling. Get needle as far down into chamber as you possible can. Set cartridge, with injector sticking out of it, and stand it up, or prop it up, somewhere with opening of injector facing up. You want this thing to free stand on its own because your hand will go numb if you had to hold it because it could take up to 10 minutes or more per chamber for ink to drain into cartridge.

Now take other injector, unaltered one, and load it with proper ink in proper amount for chamber you are refilling. Carefully fill cavity of injector that is sticking out of cartridge. Now you wait. Let gravity pull ink from injector into cartridge. At first it will seem like nothing is happening. Go grab your favorite vice, cigarette, beer or coffee, whatever hits you. :-) When you come back ink should be drained into cartridge. Rinse and repeat. And I mean that literally.