1998 E300 cranks but no start, help!

[lupin..the..3rd]

Hoping the collective forum wisdom knows the secret to solving this one, but it's got me stumped. Car is a 1998 E300 turbodiesel. Turning the key it will crank and crank until the battery wears down, but it doesn't fire at all, not even a sputter. It is getting fuel, I get fuel when I crack the injector lines, and also while cranking there is a fuel smelling smoke coming from the tail pipe.

The car has been driven daily. There was a known phantom drain on the battery, as parking it for 2 or 3 days would result in a weak/slow crank next time it was driven, but it always started. Just prior to this no-start condition, the car was parked for 2 weeks straight, and the battery went totally dead. I put it on a smart charger for a few days, and it has charged back up successfully now.... but no start.

I've attached an advanced code reader to the 38 pin plug, and there is only a single fault across all 18 modules in this car. The one fault is related to temp sensor in the transmission, and was present prior to this no start condition. There were also some "voltage too low" faults on a bunch of the modules, but after the battery was recharged, those have been cleared and have not come back.

And I had a spare Genuine MB K40 relay, so I tried swapping it, but no improvement.

Thanks in advance for any ideas!