Well the plot thickens, like black slime in a diesel tank maybe..
I was woken up at 2am by the wife throwing up (poor lass), her main concern was that she had woken me up omg, she takes consideration of others to a different level. She thinks she picked up a bug from someone at work, so hopefully nothing serious
Anyway the upshot was I spent the wee hours of the morning wondering how black slimy stuff gets into a fuel tank
A mate called round last night, he has had diesel bug in his fork lift, and it's a right slimy mess swimming in the fuel itself apparently, pretty easy to identify, so I'm pretty sure what I have is not that.
He also has an A2, and recently took out the sender, to find it was as clean as a whistle. Photos of other ones that I have seen on the forum have been fairly clean too, so I don't think it's a case of, that's just what an old diesel tank looks like.
As far as I'm aware, something can only get in the tank two different ways, either through the filler neck, or down the return pipe from the tandem pump. We've all seen the black gunk that tends to accumulate around a cars fuel cap, but does that stuff get into the tank? I guess some will.
Both my cars run pretty well once they are going, so tandem pump performance must be pretty good, that's not to say that they are'nt possibly leaking a tiny bit of oil into the return feed, I guess it would soon build up. He can correct me if I'm wrong, but it seems like
@Little Dog findings are not yet 100% conclusive that it's impossible. The black stuff does seem much more like oil than dirt and grime.