FAN 2839294 - Caterpillar

3406B Truck Engines (7FB)Description of Change: A new fuel ratio control is being introduced that is mechanically simpler and less costly than the former control. The control is initially activated following engine start-up by oil pressure acting on the components of a unique lever assembly inside the governor housing. Following activation, the control operates on manifold pressure only.Unlike the former fuel ratio control, the component parts of the new fuel ratio control are not serviced separately. In the case of a diagnosed diaphragm failure, for example, the control is readily replaced as an assembly.
Testing and adjusting procedures become simpler with the new fuel ratio control. The control linkage is nonadjustable (no "static lever setting"). Ratio control setting checks are performed dynamically. Setting changes are accomplished by loosening a two-bolt retaining plate and rotating the control housing either clockwise (more negative setting) or counterclockwise (more positive setting). Checking for diaphragm leakage or boost pressure that gives full torque rack travel is performed the same as in the former control.
Comparison of fuel ratio controls.Adaptable To: The new 7W5318 Fuel Ratio Control is initially being introduced on selected arrangements of the above truck engine. Application on other arrangements will follow. Information will be forthcoming on adapting the new control to earlier engines.