Spinning Wheels

If it can't pull its own weight, I would check the slide shoes for the middle rail.  It could they are stuck and are not allowing the wheels to touch the track.  They should be spring loaded and be able to compress with the weight of the engine when it sits on the track.  I can't see any other reason for an engine to spin its wheels when its not connected to anything else.

Thanks Joe I checked the slide shoes on the 490 and 999. The 490's slide shoe moved easily. I looks like it sits square and flat on the tracks. I noticed after looking that the wheels have a slight grove in them, not flat like I thought. I decided to take a piece of plumbing emery to them. I was afraid of making the too smooth. It did improve the 490's ability to move on it's own as well as pull a few cars. The 999 was a basket case. I bought it from Ebay (untested). I was sure that meant it didn't run. The motor was in sad shape, tape on all the wires hiding bad solder joints, broken brush holder with a glob of solder attempting to hold  it down. I decided to go all in and take it apart. The commutator needed cleaning (black), had surface rust on core plates. I found a way to sneak out the reverse unit and the armature without pulling the wheels. After cleaning it up replacing the screws and nuts, got the motor running again. I fear that this motor may not have enough power to pull much. The slide shoe on this one was missing. I used a spring from a battery holder cut in half to give it the feel of the 490. After sanding the wheels on this one it also improved but lacks the power of the other two locomotives. I thought the 666 and 999 were known for pulling power. I might have to look for a better motor. I would like to give it life again and will continue to fiddle with it even if I get another motor. Thank you for your advice it was very helpful.

Oh - spinning wheels; I thought that this was going to be about spinning wheels. 

D500 Some times I think I'm just spinning my Wheels LOL