DIY Duramax Fuel Fix: Rebuilding A Leaky Fuel Filter Head A common problem with high-mileage 2001-2010 Duramax trucks is that the fuel filter head assembly begins to develop air leaks. The engine’s CP3 high-pressure fuel pump is capable of drawing fuel from the tank without the aid of an external lift pump as long as the system remains primed. DMAX Fuel Filter Head Assembly (LB7) | DMAX Store Loss of Prime and low fuel rail pressure codes are common symptoms of a bad filter head. Includes: New LB7 Filter Head; New Nylon Bleeder Screw; DmaxStore Note: Dmaxstore fuel filter head spacer is recomended when replacing the filter head because it helps keep the filter head cooler and gives you more room to service your filter. Select from drop down from above.