On my Life Like EMD E8A, the motor runs and then just stops. I have shell off and I am touching sufficient power to the two soldered junctions on the strip on each side. It does the exact same thing with shell on and on the track. It has been lubed lightly with light conductive oil. Does this sound like the brushes are gone or is there possibly something else I'm missing?
It sounds like a brush/springs/commutator problem but first, make absolutely sure power is being supplied to the brush holders uninterruptedly. Doug
Are you analog DC, or DCC ? And, if other locos do the same then it is in your controls. If you own only one loco, what about the throttle, main power connection to the rails ?