Pull the chrome lifer cover off, use a suitably sized wrench to ease the lifter arm forward to provide slack in the cable, and remove the cable while holding tension. Ease off on the wrench, it should stop moving around 2 o'clock. How much movement now? If yours keeps going, put the cable back on for now as you definitely need to take off the side cover and see what's wrong.
New gasket and new seal (goes in the cover). I wonder if your return spring got detached somehow??
