1981 Mercedes Benz 300sd

Engine Mechanical problem
1981 Mercedes Benz 300sd 4 cyl Two Wheel Drive Automatic 200000 miles

I purged the lined with the plunger, no effect. I have noticed that if a disconnect the fuel line in, rifgt at the plastic fuel pre-filter, no fuel is pumped. I do not hear the fuel pump with the key on or when the car cranks. Shoud I hear it? Fuel does seem to pump out of the injector pump though. I suspect the fuel pump. Am I missing anything?
August 22, 2009.

It does sound like the fuel pump is weak or bad. Here is a how to for checking it. Check it out and let me know what you find.

Thanks, where is the fuel pump? CHILTON SAYS IT IS IN LINE, under the left pass floor panal, but I DON'T see it there. Is it in the fuel tank? In line next to the fuel tank?

Aug 23, 2009.
I just tried liiking I up with our online repair manual and the info isn't available. I believe the Chilton manual is correct. I don't think it's in the tank on your model.