The Benz pump does discharge with the spring which means it can be deadheaded without damaging it.
The fuel pump as it is a Constant Pressure pump, not a constant volume pump.

Just trying to understand benefits from a return-line, as it seems it is not necessary...

thanks,
manny

thinking about this...it seems that priming the system w/o a return-line (say after a fuel-filter replacement) would be more difficult.

Manny, having a return line is required, these things flow HUGE amounts back. Also there is a benifit to returning to the tank, in cold weather it warms the fuel in the tank preventing gell. When you plum your return line, make sure it reaches the bottom of the tank. This prevents the fuel from foaming and getting air in the system.

the enginers that designed the damn thing knew what they were doing.

thanks for the replies...

Fuel return-line added back to the list :)

For future search results can you please specify which pump and engine you're working on?

Thanks!

the mighty mercedes om617 - turbo 3.0 diesel

need to update my sig :D