I also found a loose spring when my paper stopped feeding from the lower tray. The advice here to look behind the middle of the roller and corresponding portion of the printer too see wher it mounts was the direction i needed.
I think my spring was modestly distorted and couldn't get it to fit suggly behind the roller and then slip other half onto the roller itself.
Here's what worked for me:
Overview: Decided to remove roller. found a straw that spring fir within and snipped a very short length - few mms - and "lightly" glued /tacked them where the spring was supposed to naturally seat. I then lightly glued one end of the spring into the printer (as opposed to roller) seat. I reinstalled the roller and was able to use finger and small screwdriver to slip the loose end of the spring into the roller seat.
1. To remove roller need to loosen plastic wrap around middle of printer. At back, there are two sets of two screws, I removed one set which let the "wrap flex"
2. slide out/remove upper and lower trays.
3. turn printer over or on side, removed one of the white tray guides(facing bottom, i removed one on left.) requires some bending, wiggling, manuevering to remove
4. "unspring" roller on that side (left) and then on right side, which requires extra bending, wiggling and manuevering as gears on that right side
5. with roller romeved, identify small "button" in center area that spring fits upon. you can just slip and lightly glue spring on it or use a little snippet of wide straw as an extra "seat" by slipping that over it, insert straw and applyu light glue. leave sping pointing out
6. on the roller, there is a little box the spring should sit in. Again, lightly glue a snippet of wide straw into the box to create a more secure seat.
7. reinsert roller, right side first and then left. Manuever loose end of spring into roller seat. make sure roller is pushed out by the spring but is easily pushed in and bounces back. this spring action is what allows tray to be removed and inserted and then have roller maintain contact to feed sheets even as paper supply decreases.
8. reinstall white tray guide - tab at one end has to go in first and then the other end manuervered in.
9. I inserted tray with half oad of paper at this point and tested (copy a blank sheet) - didn't work- kept trying to feed.
10. Filled feeder, tried again and worked. Hoping it will work at leasrt if try is more than half full. Maybe more once it kind of "settles in"
11. screwed in remaining screws.
Once I had a plan, job took about 30 minutes. Initial fruitless afforts and coming up with plan to remove roller took at least 30-60 minutes.
If you are lucky you can slip spring back in place but I couldn't and marvel that anyone could. Try for 10 minutes then try above.
Be careful not to break plastic tabs and bits - I was willing to toss it ioif I broke it.
Good luck.
