There should be a hole in the pan and rail for the spring to hook into. Just hooking it over the lip of the pan won't work, it will come off. If the hole isn't in the right place (it depends on which linkage you have) you should make a clip that bolts in the outside of the pan flange and bends around the lip with a hole for the spring to hook into. I don't think anyone makes a specific spring for this, but you can get a universal spring at the parts store.
