1. The Duramax fuel filter is located on the passenger side of the engine compartment, back toward the firewall, right next to the battery. If you have big hands, you can pretty much forget about getting to the fuel filter. Removing the plastic fenderwell exposes the filter, providing easy access through the fenderwell opening. That's probably why we were told it would cost $150 to have GM replace a $40 fuel filter. About 14 plastic snap fasteners hold the plastic fender in place, and it took all of about 2 minutes to pull them off. It took longer to fish out the plastic inner fender, due to our lift kit that holds twin piggyback Fox Shox dampers in the dual shock mount.