The older MBs use a separate piston type pump driven off the IP. These aren't too good at suction, and will take forever to get enough fuel through the filter and into the IP to purge all the air out. The IP is also somewhat difficult to purge of air, too.

The newer (60x and up) IP has an internal gear pump that produces somewhat better suction and better pressure flow, and the IP purges better, so no priming pump.

My Volvo has a VE type pump (single piston, rotating delivery sleeve, and also has and interal gear pump and no priming pump.

Always helps to fill the fuel filter before attempting to start dry, it still can take a long time to get a 603 pumped back up if it runs out of fuel or has a leak -- I've heard of the 0-ring at the pump intake leaking all the fuel back into the tank overnight and taking a long time to crank up next start!

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!