91 Mercedes 350SDL will not start! Help. Please?

My wife was driving the car on empty (reserve light on) and she stopped at the mall and went back out to come home, backed up a few feet, it died and it
would not start. Towed it to the gas station across the street and filled he up, and no change. Towed it home, and have tried swapping filters, getting new line and new clamps. Even tried the purge instructions and it still would not start with just the purge tank hooked up (no gas tank at all!) It just starts after sitting overnight for about 10 seconds and sputters and coughs to it's death. Verified all the vacuum lines are connected and the hoses are in great shape. No leaks from the bypass lines at all or any where else I can see. I bypassed the fuel pre-heater thinking that would make the fuel too warm in the 107F heat. I tested the automatic primer pump and it seems to be pumping like it is supposed to, although i have not tested teh pressure coming out it yet. Any ideas what to test next?
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Was it filled with diesel #2? or gasoline?
What's to say the problem is fuel related?
It may not be.
But let's say it is for this test. At the injection pump crack loose one or two of the high pressure lines to the injectors to see if fuel oozes from the intentional leak when the motor is cranked. If so, the motor has fuel, if not, why not. Don't over tighten these lines, just snug enough to not leak.
If no fuel at the injectors I'd check all the hose connections and filters that you've disturbed for tightness - an air leak may be the cause. Then I'd check the shut down device - if it is vacuum powered, does its vacuum line have any oil in it? If so the device is broken and may be holding the fuel rack in the OFF position.
These 3.5L diesels have a spotty reputation.
Has this 3.5L motor "acted up?" burned oil? made odd, grunting noises?
Hopefully not, but if so, there may be serious problems - with bent connecting rods and scored cylinder walls often #1 and #4.
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thank you for your reply. T.G. Lambach wrote:

to the rear, just to verify that all lines were bled. i also just did the test you suggested, on number 3 and 6 and there was fuel seepage.

connector on the rear of the pump, and if i removed it (when it was running) it would not shut off with the key. i also cannot find any vacuum lines going into the rear of the pump like on my 81 300sd.

had a bad turbo seal and leaked like crazy. replaced it with a new one and it quit smoking after about 15 minutes of driving, and has not smoked since. i also took it to mercedes to troubleshoot, to make sure it was only the turbo, and the compression cam up at 312-330 on all cylinders. the lowest readings were on 3 and 5.

anything else i can try? thanks.
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There is fuel at the injection pump BUT there may be some air inside the high pressure lines - at their high points - that needs to be expelled. The only way I know to do this is to increase the fuel volume while cranking to motor - so FLOOR IT!
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If the tank has gone dry, it is not unusual to take 2+ minutes of cranking to bleed the fuel hoses. How long have you tried?
narftroz wrote:

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If you have automatic purging like mine... then the first start is the hard start... whoo... you need to wait for glow plug to warm up, then step on the accelerator more than halfway... and crank away until it starts... don't crank more than 30 seconds at a time... let starter cool for a couple of minutes...
Once rough starting, keep pedal pressed down until engine smooth out or can idle by itself...
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