Key Brass HOn3 D&RGW C18 2-8-0 #318 - won't run - help needed

Hello,

I have a Key Brass HOn3 D&RGW C18 2-8-0, as #318, but it will not power-up or run. I purchased it 2nd-hand on Ebay last autumn, and have unscrewed the chassis from the body at one point. This involved unscrewing the drawbar from the locomotive, which forms part of the power feed from the tender. Despite touching the power leads (to the track) from my controller to the 2 power feeds (one from the drawbar, the other from the loco chassis) on the motor, the latter still refuses to power-up. Is the motor defective, or is a short happening somewhere? The motor head is encased in a plastic block on the chassis, with the feed wires passing through it.

Can anyone offer any possible solutions to this problem? My Sunset Brass C16, of the same vintage, powers-up perfectly.

Chris