If someone has used all their energy on something, but must continue, they are running on fumes. It is an expression used when driving a car when the needle is on empty but still running. We say it is 'running on fumes'.
When something is described as a rusty needle, it is badly damaged but still works, or if someone very is sick or tired but still manages to do things at a fairly good level. An alternative form is "a tarnished needle".