When I bought my MB in 1997, the fuel pump whined. It continued to do so and lasted for 9 more years.

The new one I installed in 2006 also whines occasionally.

I'm not saying to ignore it, just saying you may have a noisy fuel pump even after installing a brand new one.

I stuck with the Peirburg brand as that's what the car came with. Wiring/connections set to work with that pump.

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Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"