If you are making copies and selecting tray 4 it cannot use tray 3, so either you just expect it to print to tray 4 when using auto select for the tray or you are talking about a print job.
8*13 can't even be loaded in tray 3,it is dedicated to either A4 or Letter,the guides physically can't go past 11.8 inches. and if it tries to pick A4 when you load it you just move the guides and re-close the tray.
If you can't get it to work, you will need a technician to fix tray 3 as it would have to be physically broken.