Help me please. Fuel leak from top of tank

Hi all,
I have a 1989 GTI cab and its failed its MOT due to a fuel leak coming from the top of the tank by the fuel pump. I have looked around and cant understand something. I clearly see the fuel pump and accumulator but I have another plastic box shaped thingy directly above the fuel tank with two one pipe going to fuel pump and i cant see where other pipe goes. Its totally out of reach and doesnt seem fixed to anything and rattles around. I think the leak is something to do with this.
Can any one help me Please?

..do you mean item 19 in the diag below…??

Thats the bugger. Looks like a filter? Thanks for diagram ure a life saver.

I also have a leaky tank from somewhere on the top. What is the best way to get a look at the tank from that side? Someone told me I might be able to get a look at it by removing the back seats.

Prowler could you please repost the diagram? It doesn't seem to be showing up anymore.

If you look under the back seats there is a round inspection hole held in by 3 or 4 screws. remove that and all should be revealed.

Smudger

smudger said

If you look under the back seats there is a round inspection hole held in by 3 or 4 screws. remove that and all should be revealed.

Smudger

Great! Now I just have to wait til spring to get it out of winter storage.

smudger said

If you look under the back seats there is a round inspection hole held in by 3 or 4 screws. remove that and all should be revealed.

Smudger

…and under that is top of sender unit. The O-ring under these fails over time and fuel can leak out here when you fill the tank up. Mine did it years ok. You can still buy the O-rings for not much money at all.

Will be a cheap fix if that's your problem?

I thought mine was the o ring, it was the small 6mm breather pipe on the top of the tank that had corroded. 

Corroded being rotted off and left a hole