i have an 81 240D chassis 123 123, engine 616, bought from original owner couple weeks ago. ran great for 500 or so miles, then last night it suddenly lost power and wouldn't start. i thought it had run out of gas, and the fuel gauge was not reading correctly, so i threw in a few gallons. no luck, so then i replaced both fuel filters, and still wouldn't start. i bled the system by opening the output bolt on the fuel filter and operating the hand pump until fuel got all over the place and then some. too much? didn't have any effect.. the last time i tried to start it, i turned it over for maybe 15 seconds, gave it some gas and it started, it gave off some bad smelling darkish smoke, and quit. tried once more and it wouldn't start, turns fine, but doesnt seem to be getting any fuel. glow plug light indicates no problems, turns over strong. what should i check next? injectors? fuel pump? air in the system?

i have the chilton and factory repair manuals to work from. also i have read some similar threads here, but not quite the same, so i decided to post.. anyway can't hurt to ask.

some additional info:

- car has been running a blend of 20 percent biodiesel for last few hundred miles. both fuels are astm grade.
-i began to notice a slight, irregular (but timed with one or more of the cylinders) knocking sound from the engine just after i bought it. it can only be heard at idle, it gets either drowned out or goes away with increased rpm. i assume this indicates the injectors need to be cleaned and adjusted, and maybe valve adjustment is due, but should not cause the car to die all of a sudden and not start?
-by unlucky chance, the car died on a street under construction. they are going to tow it tommorow morning, sept 7 2004, if i don't get it out of there somehow.

i appreciate very much any relevant advice!

-jeff