POST 9:
Chuffing stopped (TMCC)
Chuffing was intermittent on my 3rd rail NP Z-5 yellowstone.
As with my GN M-2, I figured a wire got shorted out or broke.
The chuffing cam is on the front set of drivers so I removed the base plate to check out the cam assembly. The wires route through this area and over the gear box so I figured a wire is shorting somewhere in there.
I moved the wires forward to get some slack to the cam assembly.
Two screws hold the on/off cam switch in place, via a piece of brass, so the cam lobes can brush against the red button on the cam switch for the chuffing.
I put power to the engine on her back and still no chuffing so I manually pushed on the button and it worked. Wasted a good hour finding out the wires were OK 
There are two red pieces of fiber board to maintain the proper distance from the cam to the cam switch.
I thought I could remove one and lower the switch but the clearance was too tight and the drivers stopped when the cam couldn't go past the switch.
I then put the cam back the distance it was and pushed on the piece of brass holding the switch to get the cam a little closer to the cam. That finally worked.
Putting everything back together, one of the screws holding one of the valve gear came out. Fortunately, I had some really small shoulder screws with thread just at the beginning of the screw. I think the screw came out while test running her on the track so that screw is long gone (another 15 minutes looking for it, an effort in futility!).
Put her on the track and the front drivers kept coming off on the curves.
Found out there's two holes to hold the front driver engine to the frame. I used the back hole which didn't align the roller on the boiler to roll properly on the plate located on the front driver engine. On curves, the roller would fall off the plate.
That shot a full day, but, at least, all is working again!
