Won't Start, Smoke from the rear of the Engine

[ubertino]

1982 300TDT with 165,000 on the odometer (might be true, might not). The relay is clicking on for the glow plugs, the engine is turning over nicely, but combustion is not quite happening. No love from the engine. It's always been a bit fussy about starting in cooler weather, but usually it just needs a little throttle to get past the rough spot, and then it rolls just fine.

Now, not only is it not starting, but there is smoke that appears white coming from the rear of the engine compartment while I'm trying to start the car. I'm going to wait a while as the day warms up, hopefully it'll start again soon.

Any thoughts? Injectors? Anything else? The smoke has me a bit worried.