Paccar fuel filter doesn't stay full

[aaronb]

No. I'll try that. Do I have to pressurize them individually? I took the vents out of the tanks about a month ago and made sure they weren't blocked. Where the lines come out of the top of the passenger side tank there's what looks like dirty fuel. I thought that might be causing the problem. I talked to mechanic and showed him and he said it wasn't a problem. Should I replace the line and fittings for the supply line on that tank?