Have a 93 F150 with two fuel tanks. I thought I saw a thread about this before, but I can't seem to find it. Is it possible to bypass one tank and just use the other. I'm running on the front only, but it's drawing fuel from the back as well. Some say it's supposed to and some say it's not. Bought a repair manual from O'Reilly's, can't find the issue there. I would really just like to know how it's supposed to work. Any advice would be appreciated.

 

Here's a thread I found. Hope it helps. https://www.fordf150.net/forums/viewtopic.php?t=120830

 

From what I've read online, your truck should have a rocker switch that powers one in-tank fuel delivery module at a time. Built in to that fuel delivery module is a check valve that prevents flow from the other tank... If both pumps run at the same time, there's a wiring issue. If one tank is getting back flow from the other, it's a fuel delivery module (check valve) issue in the tank that is getting back filled.

 

 

This & the NEXT several pages explain how the system works:

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The links on this page will get you the most-useful service manuals:

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