gcarra1

I have a 1980 450 SL with 66000 miles with I believe to be a fuel pump issue. When I turn on the key the fuel pump starts and stop as normal and the car starts right up and runs normally. The concern I have is while Driving I hear a humming which sounds like the fuel pump is running continuously. I have gotten under the car while idling to confirm it is the fuel pump. Is this normal and the fuel pump is loud and needs replacing or is there some type of pressure switch which should be controlling the on and off of fuel pump as needed.

myway

It is normal. Pressure is controlled at the fuel distributor. Any fuel not needed is returned to the tank.