WIX Filters 33686 Diesel Fuel Filter Water Separator

The WIX 33686 Diesel Fuel Filter Water Separator is a spin‑on filtration unit designed to remove water and particulates from diesel fuel in heavy‑duty systems, protecting injectors and other fuel‑delivery components before fuel reaches the engine. It is commonly installed in Caterpillar engines, commercial trucks, construction equipment, generators, and industrial diesel machinery that require dependable fuel filtration. Key specifications include a 4‑micron nominal rating with Enhanced Cellulose filtration media, a height of 7.338 inches, top outer diameter of 3.66 inches, and a 1‑14 thread size, supporting a maximum flow of 8–10 GPM and a burst pressure rating of 290 psi. The gasket outside diameter is 2.834 inches and the inside diameter is 2.462 inches, with a spin‑on mounting and a function focused on fuel contaminant and water removal to protect injector performance. Cross references and OEM equivalents include NAPA Gold 3686; Caterpillar 1R0751; Fleetguard FF5320; Donaldson P551313, with common replacements Baldwin BF7635 and Donaldson P551313.