Abstract: A sender assembly that has a compact state, which may allow a pump assembly including the sender assembly to be easily inserted into an opening of a fluid tank. For example, the pump assembly may be insertable into the opening of the fluid tank while a longitudinal axis of the pump assembly remains coaxial with the opening. When in the compact state a rotatable arm and a float of the sender assembly may be entirely within or deformable to be within a predetermined envelope that has a radial extent less than the opening of the fluid tank to allow the sender assembly to be inserted straight into the opening. The predetermined envelope may be coaxial with the longitudinal axis and have a cross-section transverse to the longitudinal axis that matches the opening of the tank.