Hello; I have a 1992 seville with the 4.9 and when the fuel level gets to 1/4 of a tank or less the service light keeps coming on with code E46 which is a fueling inbalance problem and when it has more then 1/4 I can drive all day without turning on the service light ? any suggestions besides keeping the tank full would be a great help. Thanks
but if I'm not mistaken fuel injected vehicles require a slightly pressurized fuel tank (and fuel return line). Now if your tank had an air leak and was not holding pressure the second fuel rail may not be able to hold enough pressure.
Another theory would be that you may have a weak fuel pump that isn't able to keep the tank at enough PSI once it's full of compressable air (when the tank is low on fuel) again there isn't enough back-pressure on the second rail/return line.
I would also check the fuel filter, and injectors as well.