Dual Tank Problem
New User
Joined: Dec 2014
Posts: 3
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94 F150 dreaded tank issue.
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. 
Fleet Owner
Joined: Oct 2005
Posts: 20,786
Likes: 1,751
From: Kentucky
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.
Lead Driver
Joined: Feb 2013
Posts: 5,006
Likes: 72
From: Roseville, MN
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.
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
New User
Joined: Dec 2014
Posts: 3
Likes: 0
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?
Lead Driver
Joined: Feb 2013
Posts: 5,006
Likes: 72
From: Roseville, MN
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.
Freshman User
Joined: Jan 2011
Posts: 44
Likes: 0
From: Orange County, Ca.
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
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