At this point I'd remove the sender (yes, it's a messy job, you'll need to fold a towel up to catch all the Diesel fuel drips, I like to raise up the sender in it's hole _almost_ all the way and gently stick a flat blade screw driver between it and the hole to allow it to drain before fully removing) and plug it in and turn the key on and tip it up to test it ~ if the gauge reads full when you hear the float slide to the top and stop, then tip it the other way and watch the gauge as the float slides down again, if you tip it vertical the gauge should read below 'R' and the low fuel lamp should illuminate .

Proper testing is always important .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better