The spring pointed to in that picture is disconnected.. its only connected on the injector pump side.. the other side of the spring, the hook broke off.

What is the springs function?

Thanks!

Oh and please excuse the artwork.

 

The spring returns the throttle to idle. One symptom of a broken spring is a truck that bucks due to your pedal foot bouncing up and down on bumps.
Buy a new spring from a hardware store, it's nothing fancy.