'86 300SDL Fuel Leak at tank?

[iFire1991]

I've purchased my 1986 diesel late '09 and only had a problem with an exhaust leak and sway bar. I was able to get accustomed to the fumes going in the cabin and dealt with my sway bar by welding it, but for a few weeks now I have a fuel leak. It's getting bad.

A little while ago, I filled up all the way. I noticed that I had a bit of fuel on the snow under my car, it wasn't bad so I dismissed it as maybe I spilled a bit and it later dripped down. After what seems to maybe have been a month, it got a hell of a lot worse.

So, today I drove the car up on blocks and slid under there. Sure enough, I found a wet spot at the rear-driver's side. There's a mount for brake lines, that's where the fuel accumulates and drips from. I can't distinguish where the tank is, I know that it's behind the back rest of the rear seat, but I can't pinpoint any opening from below except for a rubber cork, which I didn't remove. I didn't see much tubing there either besides the green brake lines.

I have a lot of experience working on semi trucks as my father has owned a variety of rigs and I've grown up working on them weekly, but cars are a completely different story for me.

Has anybody else had the same issue with their fuel system?