Stripping lionel diesel engine frame

I have another question. The power truck is attached to the chassis with two fixtures that pivot around slots on either side of the truck. I note that the frame's original yellow paint is worn away in those areas. When I repaint the frame, do I need to keep these areas free from paint for electrical continunity? 

I am sure the paint could wear away again over time, but is that connection between the spring and the frame on either side making some electrical connection that would be lost if the frame's upperside around the power truck area is completely painted over?

Thanks.