GOLDEN-ARM wrote:Clogged air filters, improper rack setting, lagging turbo, etc., could be the cause. Running rich never hurt anything before. If it was gas powered, fouled plugs would result. Incomplete combustion doesn't harm the diesel, in fact, it might even be running cooler, due to the fact all the fuel is not burning. Deposits could form, in the combustion chamber, if allowed to run like this, for extremely excessive periods, but they will burn right off, once the problem is resolved. Makes for some interesting photos, though....... 
Maybe if it was a GE...
EMD's rarely run that bad unless something is seriously screwed up in it. Black means too much fuel is burning and has no where to go. I would guess it's one of three things:
1 - Turbo is shot - can't spin, can't provide the engine with enough air, and combustion gases are being backed up in the manifold. As the combustion process backs up and RPM's drop the governor is going to compensate with more fuel. This could be caused by anything too - Gear Train, stub shaft, over running clutch, internal disintigration of the turbo itself to name a few root causes.
2 - Turbo Over Running Clutch - The turbo depends on this clutch to free wheel above the sixth notch(?) otherwise the turbo is gear driven to supply adequate air for combustion (two stroke scavenger). If this pack of gears won't let the turbo freewheel and the governor is giving the motor eight notch fuel - the fuel is going to back up somewhere. Unlike GE's I haven't witnessed too many EMD's shoot flames (atleast out of the stack).
Symptoms one and two can cause blow back through the turbo which will often melt the air filters.
3 - blown power assembly. If a piston has self destructed or a valve drops - the engine will still run - even while the P.A. literally destroys itself. Now in this case the tip of the unit injector on that cylinder head could become damaged. Allowing an uncontrolled amount of fuel to pump into the cylinder and subsequently into the exhaust manifled and turbo. Some GE's where notorious for blowing the tips off the injector nozzles in the early days of electronic fuel injection, I'm told.
These are some basics. Anythings possible especially on the railroad.
"does anyone know where the love of god goes when the waves turn the minutes to hours?"
The Wreck of the Edmund Fitzgerald
by Gordon Lightfoot
