I have a Canon MP 540, which appears very similar to your MP 480, except for having a separate printhead and 5 cartridges. I think the inner workings of the two printers are very similar, so I shot some pictures inside the MP 540 using a webcam, to get close up pictures without the need for taking the printer apart.
To gain better access to the printers inner works, you could unscrew the mechanism holding the lid open and replace it with a longer prop cut from a paint stirring stick, and holding it in place using a screw, washer, 5/16" OD bushing and a hexnut. Click thumbs to enlarge.
The paint stirrer prop: and details:
The timing strip must slide through the cartridge carriage and be attached to hooks and a spring inside the printer, the job will be fiddly, but that is much better than having to remove the scanner, control panel and upper part of the cabinet. Hopefully the strip is not torn, and the coil spring present. If the spring is left inside the printer it could cause irreparable damage if it is not found and removed. Click the thumbs to enlarge.
Timing strip, left side: and strip slid through carriage: and timing strip right side:
Note "L" marking on left side of the timing strip. It must read as a proper "L" to ensure correct orientation of the strip.
Good luck with the repair and don't give up!
Peter.