I have a 89 f 250 5.8. I'm not to knowledgeable about repair but can be a quick learner. I just purchased this vehicle as a need to use weekend vehicle. I put fuel in the rear tank about 14 gal and a little more in the front tank which made neither one completely full,drove home then parked. The next morning I noticed the rear tank Gage showed almost empty and the front tank was as full as one can get on the Gage. Odd to me. Did the tank pump fuel into the other? I did not see any fuel leakage any where.Why did other tank now show more fuel?
Other question- The front tank gives me a lot of trouble when trying to pump fuel into it. The gas pump nozzle just keeps shutting off. Sure was a pain to get gas into the tank.
To answer your 1st question, there is a metering valve that changes which tank is drawing fuel and where the fuel is being returned. It is possible for that valve not to function properly thus allowing the fuel to be returned to the other tank. However, if it is fuel injected it will cause preformance problems and possible check engine light.
To answer your 2nd question, there is a restriction in your fill tube or the vent/return on the fill tube is restricted.