HI, I am trying to trouble shoot a no start on a friends 1982 320i, multi port fuel inj. 4 cyl. I found no fuel pressure in the system and disconected the fuel line at the fuel distributor to find no pressure either. I disconnected the hose to the main fuel pump outlet and cranked the eng. while still no fuel was vissable. While my friend continued cranking, I tapped on the main fuel pump and bingo, she flowed like a champ. So I figured it was a no brainer, and had him order a new fuel pump. He installed it, but still no fuel press. Now assuming he installed it properly, and yes there is plenty of gas in the tank and 12v available to pump w/ good ground, what is going on here? I am looking at a diagram of the fuel system and can see an electric fuel pump inside the fuel tank. I am unable to find any literature to explain why a fuel pump needs a fuel pump. If this in-tank pump were to fail, would that leave the main fuel pump high and dry? Any explaination of this "pre-pump", ideas of what may be the problem, or any help you could offer would be so much appreciated. Thank you.