You have the right idea but the pressure relief valve is in the fuel pump well on the right side of the tank. The valve itself is probably not the fault and it's more likely the O-rings/seal, on the left side that you say the noise is coming from, which feeds the syphon jets. If you have a look at the fuel diagram in the Bentley manual (or posted here) and pull the left side apart it will start to make more sense. There are a lot of posts/threads about this on the forum as well.

__________________
1988 325is (purchased new) sold
2004 X5 3.0 2005 X3 2.5
2008 X5 3.0 (new to me)