That would be considered a plugged, pinched fuel line....that the valve is going just enough to chop off gasoline through the front tank but not much ample to have gas from your back tank. also if I swap again into the rear tank it fixes it for about a moment https://40-ft-shipping-container24431.like-blogs.com/36226450/top-40-ft-tilt-container-trailer-for-sale-secrets