As with many other ink cartridges it is best to refill Lexmark or Dell ink cartridges just before they run out of ink or immediately after they run out of ink. The Lexmark and Dell ink cartridge print heads will clog if not refilled soon, making a print head cleaning tool very helpful! If you do refill them ontime you can often get recycle a black Dell or Lexmark cartridge 8 - 10 times and consistently get it to work if you have a print head cleaning tool available.

Tips on getting Lexmark and Dell cartridges to work after Recycling:

1) Make sure the cartridge you are using is clean with no damage to the print head nozzles or circuitry. You can clean the print head with rubbing alchohol or DISTILLED water (for reduced oxidation compared to regular water)
2) Use ink which is designed for your printer. The characteristics of the ink are important. We do not recommend using "universal" or "generic" ink for refilling all cartridges. The printing technologies used for Dell cartridges are different that the technologies for HP cartridges for example. There are often differences even between cartridges with the same brand.

3) Refill cartridges which have been used in the recent past with ink that is not more than 2 years old. Ink nozzles will potentially clog over time as the ink in the cartridge biodegrades. Use new ink and new cartridges when possible. Generally inkjet ink is considered past it's expiration date (effective use date) within 2-3 years of purchase.
4) Understand that a print head cleaning tool can be instrumental to your success in refilling ink cartridges. It is not unusual to do all the steps recommended in your refill kit and then...it still doesn't work! There are several reasons for this as noted above (the cartridge has failed electrically, or is too clogged to work after refilling...etc.) but, a print head cleaning tool for your specific ink cartridge can make a huge difference. If you can unclog the cartridge, you can probably get it to work.

Great refill kit instructions can be found at http://www.inkjetcartridge.com/refinforlexp.html for your Lexmark or Dell inkjet cartridges. will potentially double or triple your success rate in refilling HP ink cartridges.