Looking at the pictures, it looks like the spring end has popped out of the roller and is now against the body. I can't tell if it is broken at the end or just not enough side pressure to keep it in. If spring end goes back in, maybe a little bending to the side to put more side pressure on it to keep it in.
If the end is broken and the spring is not too brittle, you can tinker and unroll one loop and see if you can bend it to work. I have been tinkering such things all my life. Sometimes it works and other times you buy the part.
The parts are available on the lionel support page for this engine. Item 27/28. Looks like a standard pickup design.
The other thing to check appears to be the broken wire attached to the "Grease" screw. It shows up on other 11340 pictures. Possibly a ground wire from the pilot truck?
