Does it short out or is it an open circuit.

This may seem a silly question, but I've seen a lot of guys call every electrical failure a short.  Did you save the paper work that came with the locomotive showing the exploded drawing of where everything is including all insulating washers?  If I remember correctly my P2k Gp9 has the body held in place by the draft gear boxes going through the pilot on each end and then being screwed to the frame mount.  Remove the screws holding the coupler pockets in place and the body slips off. 

If the locomotive trips some sort of circuit breaker in your power supply system (you didn't mention if dcc or dc), then you have a short.  If it just doesn't run, it may be an open circuit.  I'm going by memory here, but I think you have wipers rubbing on the back of the wheels to transfer power from the track to the motor.  If that is the case, you most likely have lost contact between the wipers and the wheels since that was the only thing you moved.

There is also the possibility of a mechanical failure.  The P2k diesels are notorious for broken gears, and since Walthers bought LifeLike, they only warranty locomotives if the original purchaser has the original sales receipt.  If you don't have the receipt, they will sell the gears to you if they have them and can find them.  Athearn gears will interchange and in my opinion Athearn gears are better quality.  The way you can tell if you have borken gears is that the locomotive will either lurch along, or the motor will spin over, but the loco just sits on the track.

Check the wheels

I found a short in a P2K GP-30 caused by the axles touching inside the spur gear that holds them.  I think there is a small shoulder inside that should keep them separated but it doesn't do a good job.  It took a while to discover what the problem was the first time. Much easier the second time. 

If dragging the loco through

If dragging the loco through the turnout knocked its wheels out of gauge the gear holding the wheels is probably cracked.  If it still runs well it may only be cracked on the shoulder not through the gear yet but if it starts exhibiting the clunking sound as it rolls down the track you will know  for sure.  I've replaced them with Athearn SD40-2 axle gears but others say the P2K gears are cut at a different angle and you should only get them from Walthers.  You used to be able to get free replacements but after modelers started upgrading their Athearn wheels and Walthers gave out more wheelsets than they made in the first place they started charging for replacements.

Paul

Thanks for the tips

Hey guys, thanks for the tips.  This will give me something to check this weekend.  It is defiently a short because I put it on the track to run it while another train was running and my layout went dead (I haven't split it into sub districts yet).  I didn't realize gears inside of the loco could break.  I will check those wipers and see where they are at.  It's just stinking frustrating as this is the first loco that I have soldered in a decoder as its an older proto 2000 gp 9.  It worked the first time and everything, and now it's dead.  I would like to tinker with locos more, espically get into some brass stuff, after I get my layout "more finished".  I will look at it this weekend and let ya know if I fixed it or not. 

Sounds like definitely a short.

A short is probably not the wipers.  Most likely a gear.  I knew broken gears would cause the locomotive to make "herky-jerky" motions down the track, I wasn't aware of the possibility of stub axles touching inside the gear but it makes sense.

Do gremlins cause shorts?

Well, I checked my GP7 this weekend.  I pulled off the cover of the truck to look for a broken gear.  I didn't see any broken pieces so I thought I would put it on the track and see if it still shorted.   Well lo and behold it worked fine.  So, thanks for the suggestions.  I'll just blame it on the gremilns.

Do you run in dc or dcc?

I seem to think that you said dcc in another post, but I don't remember.  If so did you install the decoder yourself?  I ask because the shell fits pretty tightly on the P2k Gp7.  Make sure there are no bare wires that could be pushed against the frame when the shell is installed.  It may be that the shell is causing a mechanical connection that is shorting out and should not be there.

You might be right

Yes, my layout is dcc.  I did install the decoder my self, and yes, I strugled to get the shell on.  (I still have problems with the fan on top popping off now and then).  I will check that.  I probably need to shorten the wires anyway.  Just hate to mess with it while it is working.  Thanks.

Few common places to

Few common places to check

1st remove the axel covers on the bottom of the trucks so you can remove the wheels. check that each axel gear is tight and the wheels cant spin on the gear. if the 2 wheels can spin independintly around the axel gear you may have a cracked gear? (common on early run Proto 2000s and a possible issue on all of them) If it has a louse or cracked gear the wheels will go in and out of gauge as the loco is running and its possible that each wheel shaft will touch in the center of the gear causing a short.

If your axels looks good remove the shell by pulling the coupler boxes off, remove the shell and look for a lose wire from the truck towers, if a wire comes un soldered it often touches the led weight and shorts the loco. While in there check the electrical board or DCC decoder for a louse wire. Hopefully by now you will see the issue. if not you will have to check the wire under the motor by removing the lead weight. there will be a yellow wire that runs to the bottom of the motor and you will have to check that it did not get pinched under the weight and is not in contact with the frame. if all that looks good try swaping a decoder as see if it runs with a diffrent decoder.

not much more to check after all that work!

Good luck

Trent