I have '78 F-250 4X4 with dual tanks. On hot days especially, fuel leaks out of the filler cap on the front tank. I can't use this fuel because my selector switch will draw from the rear tank first, then from the front tank, no matter which position the selector switch is in. The vent lines on the filler tube seem like they are in good shape for both tanks. I can hear the selector switch click when someone switches the lever in the cab.

The selector switch is new to the vehicle (junkyard aquisition several months ago when I was last addressing the problem). I have read the wiring diagram and realize that the switch is spring return, with power switching to the other tank.

I can think of no other way that the higher in elevation back tank is feeding to the lower elevation front tank than to have the fuel lines connected by a partially open valve. Should I buy a new valve from the Auto Parts Store, or is there something that I'm missing?

Thanks,
Jeff

 

Jeff,
You're not transfering fuel, it's expanding within the tank. I have a '77 with dual tanks, one behind the seat and the other over the spare tire. When I fill up at the gas station I always put too much in and later in the day or the next day when the fuel warms up and warms the trapped air within starts expanding fuel will run from both tanks. This really makes the inside of my truck smell great! The problem is the vent lines within the tank aren't always in the right attitude to allow the trapped air within the tank to vent overboard. I have found on mine through experiment that if I park the left wheels on a pair of 2X8's, one under each tire, I don't have a problem any more. It's sometimes a hassle but I do enjoy having both tanks available. Remember, if you quit using one of the tanks the moisture in the tank will settle and eventually will rust to bottom of the tank. Hope this is helpful.
Gary

 

Gary,

Thanks for the info. I'm hoping that a combination of your advice and installing a new valve so that I can actually run on the front tank without first using all the fuel in the rear tank will help solve the problem. I have a similar problem on my '70 bronco, and I just have to use both tanks at first to draw a couple of gallons down so they don't expand so much. I will post back after the new valve.....

Jeff