Use the primer pump. It is located at the bottom of the IP, cylindrical shape and the top is about the size of a silver dollar. If it is the orignal it should be white and you have to unscrew it and then pump it in and out. If it is the newer version it is black and you just push it.

Pump it until you get fuel flowing through it and then pump it about 20 more times.

FYI- You may need to pump it 100 times or so to prime it.

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2009 ML320 Bluetec
1985 300CD
1981 300TD

Past Mercedes
1979 300TD
1982 300TD
2000 E320 4Matic Wagon
1998 E430
1984 300SD
1980 300SD