High-pressure fuel can penetrate skin. Always relieve system pressure (disconnect fuel rail pressure sensor or crank with fuse pulled) before loosening any high-pressure line.
[Fuel Tank] │ (Supply + Return lines along frame) ▼ [Filter Housing] ←───── (Return from injectors/CP3) │ ▼ [CP3 Pump] ├───► [Driver Rail] ───┬──► Inj 1 │ ├──► Inj 3 │ ├──► Inj 5 │ └──► Inj 7 └───► [Pass Rail] ───┬──► Inj 2 ├──► Inj 4 ├──► Inj 6 └──► Inj 8 2008 Duramax Fuel Line Diagram