If it works under USB then try creating a new printer entry in the CUPS Manager http://localhost:631/
and select 'LPD/LPR Host or Printer' under 'Other Network Printers', specify the connection as lpd://xxx.xxx.xxx.xxx/lpt1
(find the IP address xxx.xxx.xxx.xxx by looking in your router's list of active devices) and make the IP address static in your router. For example, I set up my Canon WiFi printer connection as lpd://192.168.1.78/lpt1
in CUPS. I used my router's browser interface to find out what address the router had assigned to the printer (192.168.1.78) and then I configured the router to always use that address for the printer.