It usually takes a lot of pumping on that hand pump to clear the air out. It is much more efficient than cranking the engine. Even if it leaks a bit. The problem is the engineer who specified that thin top and sharp edged "knurling" to improve grip was a sadist. If the pump is squirting Diesel out while you are operating it, you should consider replacing it. They are not expensive or that much trouble to replace.

The pump needs to operate reasonably quickly and continuously until you hear a slight buzzing sound. That is a little pressure relief valve in the system that is signaling the air is actually getting out of the pump area as you are now building pressure in the system. You can't build pressure, or much pressure, with air in there as air is compressible and the pump stroke volume is not that much. I usually continue to operate the hand pump until I have about 60 strokes of "buzzing." I have managed to do this with the unit leaking a bit. Once you screw the handle down solid, you should have nothing leaking out. If you still have a leak, you must replace the pump.

Changing the filters is messy and requires you run this priming routine. The priming is simpler, as others have noted, if you fill the big, screw on filter with Diesel first. I usually put a Diesel additive in the big filter before screwing it back on - like RedLine or one of the others as they are nearly all Diesel fuel anyway.

Good luck,

Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)