Posted by: Rolly
The fuel automatic bypasses excessive fuel and pressure back to the fuel tank. The ports in the valve are small and can become plugged with crud; pressure will rise or bypass intermittent depending on the obstruction. I would clean this valve first. If the fuel line back to the tank becomes plugged at the tank the same thing will happen. I had a fuel tank on my 1920 that was very rusted. I had to make fittings to go high above the bottom of the tank. Eventually I had to clean and treat the tank.