Having a problem with my dual fuel tanks on my 87. When the front tank is selected it reads empty and when the rear tank is selected it reads way past full. Also, when I fill both tanks and use the front tank, it pulls from the rear tank too and they'll both end up running out of fuel and I have now at to know how much fuel I actually have in either tank. Can anyone help me troubleshoot or break it down Barney style on how to check what is bad?

-1987 Ford F150 XLT Lariat 5.0 with 4 spd auto

 

What's probably happening is both pumps are running, and you are getting fuel return to both tanks. I would try taking a look at the switch.

 

That would explain the guage reading incorrectly too? I'll look at replacing the it then. Do you know if I were to hook up a multimeter what I'd be looking for?

 

I would check to see if there is continuity with the switch first. Make sure when you switch it, that one shuts off and the other gets activated.