I have been having a hard time starting my 1988 740 turbo lately. It was cranking for what seemed like a long time (10-15 seconds) before starting. I tried changing the fuel pump relay as well as Techron in the tank and Seafoam through a vacuum intake,none of which did much.

The solution, that seems to work quite well is simple. Before turning the key, I push the accelerator pedal all the way to the floor and then slowly let up on it. When the accelerator pedal is almost all the way back, I turn the key to start. Now it starts perfectly!