Lionel Legacy Troubleshooting - Any Ideas?

It seemed that when you pushed the throttle up, the amps on the transformer immediately shot up and settled at about 7.0 amps when the engine was running, which is way too much amp draw for just an engine and tender, assuming that was the only engine or drain on the track.

Do your other engines do the same ?

There is a short in the engine or tender or track.  It is drawing 7-8 amps which is way too high.  The Z4000 won't trip the breaker until around 8 amps.  

First take the engine and tender (and any other trains) off the track and advance the throttle.  With nothing on the track, the amperage should be 0 or maybe 0.1 or 0.2 AMPS.  If it goes high again there is a short on the layout.

Then put the engine and then the tender one more time on the track separately to see which one is shorted.  Advance the handle and power off if it goes above 2 amps.  Then pull the shell off whichever one is shorting.  You may be able to locate the short (pinched wire, burn marks).  Do not run the engine until the short is located.  So far at least some of your circuit boards have not fried, but I would not push your luck.  If you cannot find it easily, send it to a tech to evaluate it.

Obviously, there's a short of some kind.  At 13 volts you have 8 amps already!  I'd stop doing that until you track down whatever is shorting!

What was the current draw at your train shop?

Appreciate all the responses, very helpful information.

We put just the tender on the track and it never went above 0.9 amps.

Next we put just the engine on the track and it shot right up like you saw in the video.

We opened the engine up and noticed a burn mark on the white wire coming from the "Run - Program" switch, as you can see in the picture.

The locomotive has been dropped off at The Train Doctor for repair, will update when we hear back from them.

Well, the RUN/PGM switch has a DC ground, if that is shorted to the frame, it'll draw a lot of current as it's NOT common to frame ground!