Paccar fuel filter doesn't stay full

[aaronb]

I drove a kenworth before this that it was always full. Our local dealership said it's supposed to run full. The fuel lines run into the top of the housing so I would think it's supposed to run full.

I actually can't figure out how it runs like that. The fuel runs into the filter on the outside of the cartridge. Flows through the cartridge and then goes out the top of the cartridge to the engine. There's no hole in the bottom of the cartridge to suck up the fuel. I just looked at the extra filter I have. Looking down through the hole in the top it's hollow. There's no tube that runs to the bottom of the cartridge to suck up the fuel down there. That makes me think the housing is bad and the fuel is somehow bypassing the filter cartridge in the filter head. I don't know how else it could run if the fuel level is so far from the outlet hole. The thing that makes me unsure about that is that if the fuel gells up it'll wax up that filter and my filter gauge tops out.