1. Make sure both the printer and computer are turned off.
2. Disconnect the interface cable from the printer.
3. Make sure paper is loaded in the printer.
4. Hold down the Load/Eject button, then press and release the power button. Continue holding down the Load/Eject button until the power light starts to flash, then release it. The printer prints one page showing its ROM version number, ink counter, and a nozzle check pattern. If the pattern has gaps in its dots, you need to clean the print head.
5. To end the check, turn off the printer after it prints the check page. (from epson.com)
Be careful about repairs on these printers. Repair costs are usually more than a new printer.
Please can someone help me? I have an Epson Stylus Photo R300 printer. It suddenly will not print in black, but all other colours are OK and the cartridge shows as full. I have replaced the cartridge, done the head/nozzle cleaning procedure but still it won't print in black. When I took out the cartridge there appeared to be ink underneath although this is not the case under the other colour cartridges. Can anyone help?