Is that the pump in the tank? As I've checked this (as in just looked at it and blew it out) and it seems ok but should there be a gauze on the end of it?

Hi, first time to post here, so be gentle if this has been asked before. I bought a 1996 300tdi disco. It was laying up for a few months, ran great for a week, but then it started to loose power - loss of revs and then might pick up a little or might die. I spotted a fuel leak from the rubber...