1991 BMW Other Crank won't start

Either you have no power from the relay or there is an open in the power supply to the pump.

How would I check for that? And where can I find a fuel pump wiring diagram? I've been searching online and can't find any for my year

I would first check if there is power to the fuel pump relay. If there is, I hate to say it, but you need to access the wiring to the pump which, if I remember correctly, it above the fuel tank. You need to check if there is from the power supply getting to the pump.

As far as a wiring schematic, most likely I have one I can access, but it is impossible to copy and paste. Also, I would need the model of the vehicle. From that, I can try to walk you through it. Other than that, I would purchase a manual from the parts store for you exact vehicle. They may have to order it, but it would be helpful if you like to work on it yourself.

Let me know.