sixto,

Older model cars had a hand operated pump to purge the air from the system, but I think you have to run the starter until it starts on your car. You are trying to push air out of the system, which is compressible, and the pump stroke is a miniscule volume at each injection stroke (at 30 mph, all the injectors squirt a combined total of 1 gallon or so in an hour if you get 30 mpg). The result is that the poor starter is cranking away at the whole motor, pumping all kinds of air through the combustion chambers, when all you want it to do is pump a few cubic centimeters of air out of the injection system. The injection pump is a kind of positive dispacement pump, and when they get air in them or the discharge lines, they have a great deal of difficulty generating any real pressure.

What happens is the bulk of the air has to be pushed back to the fuel tank and what is left has to be displaced/absorbed by fuel under high pressure. The injectors are like little relief valves and there has to be enough pressure under them to lift the valve stem off the nozzle seat. With a significant amount of air in the system, you don't get that much pressure as the small injection pump stroke is designed to develop that pressure each stroke with an incompressible liquid, not a very compressible gas. So, it can pump the air back to the tank, but that is a long way, and it takes a lot of strokes which means the engine has to turn over a lot of times. Stopping and starting is a little like taking three steps forward and slipping two steps back as once the pump stops pumping the air will tend to go back to the top of every one of the little loops in the injector tubes and anywhere else. It also relieves the pressure in the injection lines to the injectors and any headway you made getting the air to dissolve in the fuel is undone, a lot like taking the top off a bottle of coke and having the gas come out of solution.

So, you have just crank it for quite a while. It is a strain on the battery and the starter. Someone here suggested doing these things with the engine warm to help the process along. Good luck, Jim

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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)