Since purchasing (new) my 86 F-150 302EFI with dual gas tanks, I have had a problem every couple of years with failure to feed gasoline from one of the tanks. Usually solved the problem by replacing the frame-rail mounted "fuel reservoir & valve". However, replacement of the valve day before yesterday did not fix the failure to feed. With the dash-mounted selector set to the rear tank, the gas gauge does not work but gas feeds from the tank and the truck will run until the tank is empty. With the dash-mounted selector set to the front tank, the gas gauge works but the truck dies as though no gas is being fed from the tank. This is complicated by the fact that occasionally the front tank will feed gas (I set the selector to "front" every so often just to try it and occasionally it works). I did replace the fuel pump a couple of years ago and replaced the fuel filter also but these do not seem to be likely culprits or neither tank would feed. Wonder if the selector switch or its electrical line has some corrosion or a break in the line that could be causing the intermittent problem? Sure would appreciate some assistance.