Yes, there is a spring in the assembly - here's the pic, dimensions as follows:
Length: .825", ground flat on both ends.
Outside diameter: .9875"
Inside diameter: .771"
Coil (wire) thickness: .106"
You'll need to buy or fabricate a compressor to depress the top cover plate under this spring's pressure in order to push the keeper in place. A little cumbersome, but have patience -
Regards,
Steve