When you put the brushes back in you got to make sure you have the proper spring tension on them.
Try backing off on the brush plate screws a hair. If the engine runs then the brushes are to tight on the commutator. Or the tension can be the opposite and do not have enough tension on the brushes too.
Try first backing off the brush plate screws a little and then try to run it.
Also make sure the lever on the e unit is making contact when you move it.
Edit.......A copy and paste you can try.
The basic wiring of the AC motor is power runs to one side of the coil, through the coil, from the other side of the coil straight to one motor brush, through the motor and back out of the other brush.
One would normally find that the center rail collector powers one side of the coil, and the second brush is 'earthed' to the chassis, and therefore to the outer rails.
To bypass the reversing unit, use a length of wire with a crocodile clip at each end. Clip one end to the coil (the side that isn't connected to the center rail pickup), and the other end to the brush holder that isn't earthed to the chassis. The motor should then run, irrespective of the reversing unit.
Congratulations! I've had to take down and clean a few e-units (my stuff is all '50's vintage American Flyer), so I understand the nervousness it brings on. Having done one, though, you'll be a lot more confident on the next one.
That's good. It's not fun. Normally I just clean the drum surface without removing it. It's always good to have an extra around and a whole unit. I did fry a motor when a drum end pin broke. This is what I first check when I find a problem.
Favoring NJ, ED, I bought parts from East Coast train Parts who attended alocal train show. There are many parts people, you may find one closer. A Stan Orr out of NY andDR Tinker in Mass if he hasn't retired.THen Jeff from the traintender is the CTT favorite. The Olsen's in Michigan too. Google and you will find.
How many swear words did you spout, while putting the E unit back together????? Aren't they such a joy to re-assemble!! As far as finding E units, they are available from a few that T-Man mentioned, but I went a different route, and bought a "junk" lot of 11 e units, and with my junk parts, I now have 10 rebuilt units. The most common one for Postwar steamers uses the 100-25 E-unit.