fuel spill -leak - aggravation

[Desert Panther]

Filled up the SD the other day when diesel fuel was at the cheapest price I'd ever seen it (1.61). I noticed that when I opened the fuel tank cap, it was pressurized slightly, as I actually felt air rush out of it. I said to myself "This is odd". It was less than a quarter full at that point. I filled up the tank completely, so that fuel was visible in the filler neck.

On the drive home, it was a nice day, so I had the windows and sunroof open and could faintly smell that distinctive diesel fuel scent emanating from somewhere on the car.

Arriving home, I lifted the hood and noticed that cylinder #1 injector was soaking wet and diesel fuel had dampened the return line. Line didn't seem to be fitting very well, so I put a cable tie around it thinking that was the source of the leak. Parked the car overnight. Upon walking out to the car this afternoon, there was a HUGE puddle of diesel fuel underneath it! Like, gallons worth! The car was sitting in the sun and it was about 88 degrees.

Looked under the hood and diesel fuel is steady stream trickling from the injector, down the side of the engine and cascading onto everything below it and finally hitting the ground. What the heck? How can this happen if the engine isnt even running? I then opened the fuel cap and again, air rushed out, suggesting it was pressurized. This greatly lessened the fuel leak but didn't stop it. My neighbor came over and found that the injector return line was actually split towards the end, so my zip tying method of temporary repair wasn't effective in the slightest. He cut the split part of the line off, shortening the line and re-installed and its holding now. I am parking the car and leaving the fuel cap loose until I get this problem straightened out. That seems to stop the pressurizing of the fuel system and consequential leaking.

Ok, so I am thinking the vent for the fuel tank must be clogged. I've heard of vents clogging and not allowing air into the tank, thereby imploding the tank, but i'd not previously heard of this scenario affecting my car before. Have any of you? I searched the peachparts catalog but found no listing for a Diesel W126 fuel tank vent valve or anything similar. What gives? Is it called something else? What do you recommend? I have other means of transport so this car doesn't "need" to be driven daily, but obviously I'd like to get it going again. Please advise. Many thanks!