1956 ford customline starter problem

[56yblock]

hello everybody, I have a problem with my starter on my 1956 ford customline,it won't start
I changed the solenoid by a new , I removed the starter from the car, I cleaned it, I checked the brushes they are still good, I tested it with a battery, it runs well, i put it on the car, and nothing, it doesn't turn , do you have any ideas?