Have a pink Williams girls set with Hudson engine that lockups when power is shut off causing freight cars to fly off the track- the engine has has a fly wheel and should coast some what. Linkage is not binding - any help would be appreciated.

I have tried two of these water pumps and have not been able to get the pump to work.
I am using DC and the hums, but no action.
I am sure I am doing something wrong.  Need serious help