91 400 LS all stock. Trunk open with panels removed, facing the gas tank there are 2 attachments on/in the tank, electric leads attached to both. It's the one mounted veritcally on the face of the tank with 2 separate leads attached causing a distinct buzzing sound, audible even in the drivers seat. Dont have a shop manual yet, so please someone enlighten me. Thx.

Hal

 

Some fuel pumps just buzz. The pump on my MX73 Cressida was audible inside and outside. Some pumps get louder the harder they have to work too. You may check/replace the fuel filter and if necessary, pull the pump to inspect the screen for debris.