Mpc era diesel appears to run slow

What kind of vertical play is there? (shim on top the arm plate or adjust screw till there is a hair gap(not tight, it limits bounce, does not hold tight) Brush springs pressure good too?  Try to feel for field coil looseness to the frame/ poor common chassis connections.

Fixed the e unit...how? Replaced contacts? What's their pressure like?

Sometimes the cap can be twisted slightly and tightened. Does this change anything? Can the armature plate be shifted L or R slightly? Does it help (I look for a new one, some have luck with it not slipping again, some with CA glue, etc.)

Measure ohms on the field coil, look for red to green continuity (should be about equal ohms and no r/grn cont. once the common end is seperated)

Armature should read equal across all plates, no cont. to the shaft.

I will do the checks you suggest tomorrow when I get home.  Thanks!

Which cars? If they are the heavyweights its quite a load for a MPC GP engine. Run the engine with the motor to the back, that will help. You said you cleaned the motor, did you adjust the armature screw? It should have just enough play to turn freely. I'm assuming that you are asking about a GP engine here.

Yes, I believe they are they heavyweights.  They are not the steam liners.  

I'm still going to do the troubleshooting above . I want to make sure the armature is installed correctly and all the coils are showing the right resistance and continuly.

I actually failed to reference the 2wire field is for the 2pos eunits, and the 2pos. e unit wouldn't have the  same type eunit from what I've seen before, though a drum type 2 pos might be possible. (2pos works off a rocking guide point being rocked left or right of plumb each cycle)