tdi in tank fuel pump

[tdi-man]

any body any ideas what the pump in the tank does ? and what happens when they start going faulty ?

thanks

 

[Khufu]

It is a combined unit, part pump & part fuel level sender. It, well, pumps fuel to the engine LOL. Not sure, but I guess on a diesel it will prime a 2nd high presssure pump in the engine bay? A faulty pump often comes up with a vcds scan, also manifesting in missing or poor power/slower acceleration.