IP network printer doesn’t print

I've got a MacBook AIR (OS X 10.9.4) and a rather old Canon MP620 printer. The printer has been successfully connected to the WLAN (PING, shows that everything is fine). The printer can also be selected in the printer menu.

Nevertheless, it simply does not start to print. I can see that the print command is being processed and then nothing happens.

The only error message I get from the console is:

13.07.14 13:47:17,714 Canon_MP620[2162]: The function `CGContextErase' is obsolete and will be removed in an upcoming update. Unfortunately, this application, or a library it uses, is using this obsolete function, and is thereby contributing to an overall degradation of system performance.

I use the LPD protocol, the IP-address of the router and leave the queue box empty.

Has anybody got an idea?

Thanks for your help!