Sorry if this has been answered elsewhere, but I've not seen this exact situation. I only run the front tank on my truck, but I've noticed that after I've driven a while I have fuel dripping from the top of my REAR tank. What is going on and how do I fix it? And please dumb it down for me.

 

What year/model/engine truck do you have? The answer depends on those details.

 

The post you tacked this to is dealing with the exact same thing. The check valve in the FDM in your rear tank is bad. When you run on the front tank you are pumping fuel into the rear tank. If you never take any fuel out of the rear tank, it gets full. When you keep pumping gas into it after it's full it leaks out.

Replace the FDM in your rear tank and it will solve your problem. Or just use the rear tank enough to keep it from overfilling if you just want to limp along for a while.

edit: I'm assuming you have a gas powered truck (you said it was a '94). If it's a diesel then I don't know much about their fuel system

 

Sorry about that, got a little frustrated. It's a 94 XLT with the inline 6 cylinder.

 

Well I just switched the tanks over, and the rear shows empty. I know that gauge works because I filled it before I was aware of my leak issue. When the leak appears, it's only after I've been driving a while, and I don't think it could be the front tankk filling the rear to the top, cuz the front tank holds less, and there's not a huge drop on the fuel gauge. Could it be a seal or something?

 

Could be that you have a leak in the fuel return line to the rear tank but before the check valve. So rather than filling the rear tank it's just the line leaking onto the top of the tank.

 

I have same problem on 97 F250HD 460. I replacing the dual tank function reservoir that is mounted on the frame rail. I have to locate the correct one first though. Not even sure I'm calling it by it's right name, too many models came out that year and some items on my truck are for a diesel model. Mine is gas with that great 8-10MPG. But it hauls a lot of wieght, even runs better w/2500LB loads. Haynes finally came out with a manual for the HD truck. #36058