Okay someone please, please explain to me how the w124 fuel system works... I just apparently can't get this straight..

So everything was working great except for my fuel sender when I got the car, last month the hose from the tank to pumps started leaking, replaced that and the screen at the bottom of the tank as well as the vent valve. I put the two smaller hoses on the bottom of the tank backwards so I had gasoline shooting out from the engine bay.. Switched them back and put everything back with a vent valve and everything seemed okay. The last few days I noticed my sender was acting really funny, didn't think much of it because it didn't work right to begin with... Went to the junkyard today and pulled a sender off, paid for it and went to put it on to find out it failed completely because the tank collapsed in on itself, the sender isn't in the right position and I need a new tank. Tank I can get..

But I want to know WTF caused this to happen, it seems I cannot get rid of a gas smell to save my life on this car and I've had nothing but problems with this fuel system! Thinking about getting the tank tomorrow I just don't want to put it in then low and behold it does this again... please help...

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76 MG Midget
78 Datsun 280Z
86 Peugeot 505
01 Subaru Outback

“Owning a car is like owning a dog. Every now and then, it craps on the carpet — but it’s still your dog.” - Jeremy Clarkson