prewar 9e wiring

Hello all,

I’m new here but I have been working on lionel products for my fathers train store THE CORNER TRAIN STORE, in Culpeper Va. for about ten years. Recently a gentleman brought in a prewar lionel 9e electric with the old style two position e-unit. The problem that I am having is that the unit is switching back and forth but the motor is only going in one direction and just humming in the other. I have restored all the old wires in there position as found but there seems to have been some work done on the motor before I received it. I guess my question is does anyone have a diagram of this old two position e-unit to see if a wire has been removed.

Thank You if you can help me.