The fuel pump (the one under the driver's seat) on my '89 740 non-turbo makes a buzzing sound that is a little louder than it should be. Especially so when the tank is nearly empty. The car runs great and makes good power. Is this the sound of impending doom, or nothing to really worry about?

I still go with the intank pump, or the short section of hose as described in the FAQs. The fact that you get this when fuel tank is low strengthens this argument. I would guess if its the FPR, then the fuel pump would be noisy at all levels.

Check your fuel pressure regulator. The FAQ has the procedure. It's easy to check proper function by removing the return line from the fuel rail, attaching a hose (clear is good), insert into a container, and then starting the car. If fuel flows through the line at a quick rate then the FPR is doing its job. Just be careful since you're dealing with gas.

My '94 945T had a buzzing main fuel pump (under the car), changed the fuel filter which didn't solve the buzz. Planned on changing the fuel pumps... Decided to follow the FAQ and check the FPR. No gas flow. Installed a new one in 15min and the buzzing went away.

Good luck. Report back with what you find.
Bean
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'80 242GT 91k, '94 945T 110k

Probably dead intank pump.. Look above, click features, then 700/900faqs. Go to Fuel. You'll see all the info, troubleshooting etc.. Car will run with dead intank pump, but not the main pump.