Vehicles with two or more fully operational fuel tanks or gas tanks are not subject to the LPFET (low pressure fuel evaporative test) or EVAP test. However these vehicles are not exempt from the EVAP (charcoal canister) visual inspection.
A smog technician will still need to locate the charcoal canister and ensure it is properly connected and not damaged. LPFET exempt vehicles are only exempt from the "functional" EVAP test which utilizes the LPFET machine; the machine is connected to the gas tank filler, the tank is pressurized and the machine detects pressure drop.
Converting your Ford Super Duty to a single tank will cause issues with the smog check if the conversation is not done properly, if it can done legally at all. If your Ford's exact year, make and model came equipped with a single tank version you will be able to convert your dual tank setup to a single tank if using the exact components of the single tank system. All EVAP connections and components must be present and match that of the single gas tank setup.
