First things first, you said the pack was brand new, it won't really "come alive" for a few runs.
Second- find someone to rebuild your motor properly, or replace the armature and brushes with new parts.
Are you running the motor that came with the car?? if so just go and buy a new motor, from experience RTR motors usually only last from 10-20 battery packs, sometimes less, sometimes more, but mostly 10-20 runs.......