Which of the following is NOT a function of a mobile fuel system?

The function of a mobile fuel system primarily involves activities related to the management and distribution of fuel to an engine. Supplying fuel to an engine is a fundamental role of these systems, as they are designed to ensure the engine receives the necessary fuel for operation. Venting excess pressure is also a critical function to maintain safety and efficiency within the system by preventing potential hazards from pressure build-up.

Feeding fuel to auxiliary engines is another function that mobile fuel systems can manage, ensuring that additional systems within the vehicle, such as generators or equipment powered by a secondary engine, have access to the necessary fuel supply.

While mobile fuel systems are integral to the overall operation of a vehicle, propelling the vehicle directly is not a function of the fuel system itself. The propulsion of the vehicle is specifically the role of the drivetrain and engine. Therefore, the function that does not belong to the mobile fuel system is the one related to propelling the vehicle, as this falls outside the scope of fuel management and distribution.