The residue that was clogging the gears in the pump housing of the Lionel Model #6-24224 water tower proved to be too much for the water and dishwashing detergent remedy that was recommended. After several failed attempts, it was necessary to remove the tank from the base in order to get access to the pump housing.
Careful when doing this as there are 2 small black rubber grommets that will need to be removed from the 2 long retaining screws that hold the roof of the tank in place. In addition, there are two surgical tube hoses that are connected to the pump assembly. These will need to be disconnected before you can remove the tank from the base and gain access to the pump housing.
The pump housing is mounted to the base by 2 screws. Another 4 screws hold the pump housing together. Inside the pump housing are 2 plastic gears. These needed to be thoroughly cleaned as they were clogged with residue from the colorant that came with this unit. I concur with those who advocate not using the Lionel colorant. It contains sugar which eventually hardens and prevents the pump from functioning.
Once the gears were cleaned and everything was re-assembled, I added distilled water with blue food coloring that contains no sugar. The water tower is now working as designed.
I hope this post helps others who experience a similar problem.