553-8165 Common Rail Fuel Pump Assembly for CAT C4.4 Diesel Engines The 553-8165 (5538165) fuel pump assembly is the high pressure common rail unit listed for the four cylinder CAT C4.4 diesel engine. This page confirms the official assembly name, separates the three fuel systems that share the same engine badge, and identifies the low cost lift pump that is frequently quoted in place of this high pressure unit. Key Features Fuel pump assembly for the common rail build of the