What is wrong with a Chevy pickup auto when you are replacing the fuel pump how do get rod behind it to move in fully?
The fuel pump retaining ring may be rusty or corroded. You may need to use a pry bar or other tool to pry it off.
Another possibility is that the fuel pump is not seated properly in the fuel tank. Make sure that the fuel pump is fully seated in the fuel tank before you try to install the retaining ring.
