I need to know if your truck has California/clean fleet emissions on it. The glow plug systems work different. If you have California/clean fleet emissions then your truck will have an EGR valve, a belt driven vacuum pump, and several vacuum control solenoids on top of the fuel filter.
If you have California emissions then 1 or more glow plugs are bad. If you have standard emissions then the glow plug controller/relay is bad.
You do not have to be from California to have one of these trucks with clean fleet emissions, I see them here in Georgia a lot.