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. 6 Duramax Fuel Filter Replacement & Water-Separator • Optional - Attach a small section of 1/4" fuel hose to the water-fuel separator drain valve located at the bottom of the fuel filter. Open the bleed screw at the top of the fuel filter housing, then drain the water separator into a suitable container and properly dispose of the fuel. • Close the drain valve and remove the fuel hose.