Hi there, I have a 1993 240 that is making a buzzing-grinding noise in the back, I think it's the fuel pump, the noise comes from under there.
My question is, do I have to change the in tank pump too, or the one near the fuel filter would be enough.
Thanks for any advice.

 

No reason to mess with what ain't broke. The two are not related.

 

Lots of times one pump loses abilty to pump and the other soon follows because its doing the work of 2.
If thats the case, and it often is, replacing one pump will cause the new pump to fail again for the same reason.

 

Except that if one pump "loses the ability to pump", the car won't run at all, so the second pump won't have a chance to get "tired" as it were...

 

From the FAQ at brickboard.

"
Fuel Pump Noise.
Fuel Pump Noise.

[Response : Peter James] I would agree the intank pump has failed and you are now stressing the main pump, which in turn can lead to premature failure of the main pump.

[Response :] Are you sure it's the in-tank pump, not the main pump down by the rear wheel arch that is making the noise? Most commonly this pump makes this noise not because it is failing, but because the in tank pump is not supplying the fuel to it for some reason. It won't do it any good to operate in this condition, and when the main pump fails, you're stuck at the roadside. : "

It happens often enough to make it into the FAQ.
Mine only has one pump , but it costs twice as much so theres no savings.