Older TMCC system was fine until track changes, now erratic

Have you got something out of phase? Re-check all your connections. Something happened when you re-wired.

That is the opposite of GATTWP(Generally Accepted Toy Train Wiring Practices).  You actually had it right before.  You always want good track joint connections.

Get rid of the water pipe connection unless you are overly concerned about protecting the layout from direct lightning strikes.

"Get rid of the water pipe connection unless you are overly concerned about protecting the layout from direct lightning strikes."

I think that's what he's using for TMCC signal reception, nothing to do with electrical feeds per se.  

While you may be seeing 17 volts on the track with a VOLT meter you may not have proper feeds to deliver the necessary current to run the trains with the "new" hookup.  If the trains are current starved they won't run.  

If there is a TMCC signal issue they may not run either BUT the lights on the engines should be rapidly blinking or providing some other cue that there is a signal propagation issue.

The water pipe is intended as ground for the TMCC signal.

If current is an issue how can it be measured?

Yes the head lights blink rapidly when acting up so there is a signal issue. Where to go from here.

Thanks for the responses

Current is measured with an ammeter but you need to have flow to measure so no flow, no measure.  Typical locomotive will pull 2-4 amps (depending on type/number of motors/sound/smoke/lights).  If you don't have enough "wire" to handle the current the device will a) stall and b) something is probably overheating from trying to pull 2-4 amps through wiring/track connections that can't handle that.  

This sounds more like issues with the command signal?  Will the trains run fine in conventional?  If they do then current capacity of your new wiring is less of an issue and TMCC signal is more likely the culprit.  I'd look at how/where the wall wart transformer is connected to the house wiring and how the "antenna" wire is run from the command base to the track.

Disconnect the "ground" to the water pipe.  If the electric panel ground and neutral are at or near earth ground(and they should be) then you are quenching the TMCC signal propagation.  TMCC depends on the potential difference between earth ground and the running rails, and you have short circuited the scheme.

I think he's running his "ground" next to the tracks, not connected to the tracks.  This is one of the recommended methods of getting the airborne component of the TMCC signal to the locomotives. 

Obviously, this "ground" should NOT be actually connected electrically to the tracks.

Well, I re-read that, and now it appears he may actually be shielding the signal if the earth ground is running along ALL the tracks.

I'm presuming he had the problem before laying the ground signal.  If he hasn't tested with it disconnected, I'd agree that disconnecting it to see if that changes things would be a good idea.

Hey fellows to clarify: The ground wire is a single 14 guage wire that runs underneath the layout. It attaches to a cold water pipe and is not connected in a loop, or to anything else for that matter, and it follows the general direction of the tracks. It is the same before and after installing new track, but, some months ago, things ran well without it. I know, don't fix it if it isn't broken. Just trying to improve with technology. I disconnected it today but alas life took me away to other things and haven't tried it out. Will let you know as soon as I can get back to it.   bruce

Removed the ground wire went from bad to worse. Think I'll start over.

I would have been surprised by any other outcome after you described the wire and how it was connected.

Where do you have the "U" connection from the command base hooked up?

How are the cab-1 batteries?

U goes to track "U" on TPC400, which goes to outside rail. Batteries are good

Do both outside rails get a track feeder? maybe try jumpering a few  outside rails together  with a piece of wire (alligator clips if you have them).

Sometimes  track configurations  can create insulated sections via switches (turnout)

I'm going to work on that. Thanks to all who have responded. At this point I believe my problems stem from "limited" feeds to the track combined with dirty track joints. I can easily add more feeds (just time consuming) but how on earth can I get those joints cleaned up? I'm using Atlas track and joiners. Most of the track is attached to the base and surrounded with landscaping which means pulling up the track to get to the joints thus risking injury to the track and certainly to the landscaping, ballasting, etc. I know there are spray compounds that can be use but I'm suspecious that they really don't  do very much. What do you think?