Cummins 4BT – Air Fuel Control (AFC) Malfunctions

The RQVK governors are equipped with an air fuel control (AFC) device to help control emissions. The AFC regulates the fuel to air mixture by sensing manifold pressure.
A malfunction of the AFC can cause low power or excesยญsive exhaust smoke under load. Leaks at the fittings or a
restriction in the tube from the intake manifold to the AFC can also cause low power.