Here is the parts view of your locomotive.
http://myflyertrains.org/gallery/album209/303_2

Remove the brushplate (#21) and turn the armature by hand. You may need to lube the gear in the loco and oil the wheel bearings until everything turns freely.

Unsolder the wiring from the tender to the locomotive to isolate the motor from the reverse unit. Reassemble the brushplate and power up the motor as previously posted to see if it runs.

If it still does not run, you may have a bad motor, possibly the armature.


Larry