First thing I'd try is soak all the sections in water with detergent for a couple of days, toothbrush it thoroughly, and then rinse with clean water.

If that doesn't work, Spray with isopropyl alcohol from the drugstore and let it set a while, Toothbrush it off, and then rinse with water.  I would test this method on one piece of track first to make sure it doesn't affect the plastic adversely.

One thing everyone forgets is the rail joiners. I would plan on replacing them, you'll never get them clean up inside and you'll never have good contact.  And don't forget to really clean the Underside of the rail where the joiners go.

Agree with Jeffrey.  I had a hard time, figuring out what the OP was trying to say.

Test with another track connection cable.  And make sure the the plug prongs are clean.  The cable itself is an often overlooked trouble location.

The correct railroader's term for this "delta" track arrangement is "wye."

If you damage the truck pin extracting it there's no loss at all.  You just have to fill the hole with styrene rod. Scrap plastic sprue from kits is perfect for this job. After the cement sets, re-drill with a pin vise to take a 2–56 screw.  If you use the right size drill, you don't even need to tap the hole, the plastic is soft enough to take the screw .  It's a much better mounting job than the cheesy plastic pin Bachmann used to use in the Jurassic.

If your time and money is at all valuable to you, you should send that engine to a professional to straighten out.  Unless you really like backfeeding each individual circuit at a time to see what works what, burning the LED headlights out because you got the polarity wrong, and re-soldering half of it because you didn't get it right in the first place.

If you really want to identify the circuits, I've heard people say that you test each pair of wires with a 9 V battery.  I've never done that though .  I despise electrical work and soldering of any kind, and I would much rather be running my Railroad than running down blind alleys trying to figure things out.  You'll probably spend about $100 if you send it to a professional, but you'll have two or three evenings back, no heartbreaking errors, plus something that's done right the first time.

If the train is for kids, the conversion car is best.  They won't be doing any switching or any consist changing or anything. And if one of them actually gets interested in real model railroading in the future, they can convert the older couplers themselves then.

Doneldon was possibly the wisest of all posters ever on this forum.  He's been gone a good many years now, but his advice is still here and still solid gold.  I cannot add anything to it.

However, there are electrical gurus here who can help you with this.

[quote author=jward freight car couplers on something like a Silver Series car or Roundhouse kit are far easier to deal with than changing a locomotive coupler. On these freight cars, it is a simple matter of unscrewing the coupler cover, changing the coupler, then replacing the cover. On a diesel locomotive, the same conversion involves threading the replacement coupler through the locomotive pilot and holding it in place while dropping the coupler cover into position in a tight space, aligning it, then dropping a screw into the same tight space. It's not that hard to do for somebody like me, but it is infinitely harder than a freight car conversion.
[/quote

All good points

https://hdl.huntington.org/digital/collection/p16003coll4/id/1531

That's what I would do.

Have you tried the locomotive on another layout?

Bachmann service dept

And go back to X2F?

😳😮😱🤯

What's wrong with the plastic trucks?