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Did I really need a new fuel pump?

I own a 2002 C240 Mercedes with 22,299 miles. After my last regular service, I began hearing a high pitched whine while driving. It got worse, I took it in & M-B people diagnosed fuel pump was making the noise & replaced the left & right side fuel pump with sending units & said noise was eliminated. When I picked up car, noise started as soon as I turned on ignition. Car went back to mechanic, returned OK. Did I really need a new fuel pump?

Was it returned and said to be OK? Or was it returned and the fuel pumps were silent? You let them replace both pumps (didn’t know each side of the tank had it’s own pump)? Couldn’t they determine which pump was making the noise? What did they tell you was the cause of the same noise when you picked up the car after it was repaired? Was the situation adaquately explained to you?

it has been my observation that MB have very noisy fuel pumps as a class. I find this expecially noticable if I have to sit in the back of one as passenger.

I’d assume they did a fuel pressure test to confirm that they are working correctly. That is what was passed, not a noise test I presume.

Odd. Fuel pumps (at least in-tank ones) should be almost silent. If you keep the tank 1/2 full or more it will be quieter.

In most, if not all, cars, the fuel pump will run a couple of seconds after the ignition key is turned to ON (RUN); then, the pump turns off. Did the noise last more than a couple of seconds, with the engine off, key in RUN? If yes, then, the problem was with some other electric motor.