my buddy has a 87 f250 5.8 fi he had 2 gas tanks one tank works good but when he switches to the other tank he can run about 15 miles and then it runs out of gas and he has to switch back to other tank. he gets about 10 miles to the gallon so we dont think it is the fuel pump because that is about 1.5 gallons of gas but we dont know for sure. has any one had this problem before? or can any one help us please? thanks in advance.





86F150 4x4 supercab long bed XLT Lariat 5.8 HO

 

The return line could be dumping fuel into the opposite tank due to a faulty dual function reservoir or misplaced fuel lines if they were previously worked on. A Haynes book will give all of the tests and checks for this

Hope that helps.

Dan

 

I have a 1988 with the same thing. I just replaced the fuel relay because I did not have any power going to the fuel switch for the pump. The low pressure pump ran, I could hear it because there was no fuel in the tank. I think now I have a bad low pressure fuel pump and it is taking out the fuel relay.