Ford: Gas guage, dual tanks, gas gauge

Question
QUESTION: I have a 85 ford f150 302 w/ dual tanks.  The front tank works, guage and pump.  When i switch over to the rear tank the pump works, but not the guage.  Why would the same gauge work for the front tank and not the rear.  So i bought a new sending unit and fuel pump from advance. After installing the new unit i still cant get the guage to work. So I ran a ground from the battery terminal to the gas tank, thinking i may have lost a groung and that didnt work. What are my other options of getting the gas gauge to work for the rear tank.  Thanks, William
ANSWER: William, I have thought long and hard on this one.  And it finally hit me.  I bet you used the old float/float assembly.  If you did, then that is your problem.  Your float is probably taking in gas, keeping it weighed down.  Good luck, Jason

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QUESTION: Jason, After replacing eveything, wiring, guages, and ect. I finally took a chance in replacing the new sending unit with anouther, and it works.  The first sending unit from advance auto was bad.  Now i have anouther problem.  When both the front and rear tanks are full. I started using the rear tank first.  Empted the tank until it got to a 1/4 of a tank and switch over to the FRONT tank.  While using the FRONT tank i notice that the guage was droping rappedly compared to the rear.  Half of the fuel was going to the motor and the other half was going to the rear tank, i discovered this when i swithch back to the rear tank discovering i had almost a 3/4 tank of gas when i ariganaly had a 1/4 of gas before swithching to the front.  What could be causing this? Is thier a check value or something.  I coworker told me that he had a 87 that did the same thing, and after spending a fortune he never got his fixed.  Thanks, William

Answer
William, I have thought about this one for a while and I have asked people that have more experience in dealing with duel tanks.  The only thing that comes to mind is the fuel transfer cylinder.  This part rarely goes out, but it does go out.  If you trace your fuel lines you should find it on the inside of the frame.  It is a four way transfer box.  It can be very expensive, so please don't go out and buy one based solely on my advice.  I am sorry I couldn't be of more help.  Good luck,   Jason