My '91 740 (non turbo) has only a tank pump. It has the Bendix "Rex Regina" ignition and fuel management system, not the typical Bosch system.

If your car has the "radio suppression relay" (which is under the hood), you should be suspicious of it.

I resoldered my fuel pump relay when it failed and left my wife stranded on the highway. Two weeks later, the suppression relay did exactly the same thing with exactly the same results. I resoldered it, too. In fact, I resoldered EVERY relay I could find in the car.

That was two years ago and everything has run fine since.

The suppression controls power to the injectors. If this relay fails, the injectors are dead.

Near the suppression relay, under the hood, you should find an identical relay (which is for the electric fan). In an emergency, and also as a good diagnostic, you can exchange the fan relay with the suppression relay.
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Don Foster (near Cape Cod, MA)