a valve in the central bore of the body. Fuel pressure provides  the force for moving the diaphragm. The diaphragm is  enclosed by a cover that retains the diaphragm loading spring.  When the valve is down against the lapped seat in the body,  the fuel lines to the cylinders are closed off. The valve is  drilled for passage of fuel from the diaphragm chamber to  its base, and a ball valve is installed within the valve. All  incoming fuel must pass through a fine screen installed in  the diaphragm chamber. From the fuel-injection control valve, fuel is delivered to  the fuel manifold valve, which provides a central point for  dividing fuel flow to the individual cylinders. In the fuel  manifold valve, a diaphragm raises or lowers a plunger  valve to open or close the individual cylinder fuel supply  ports simultaneously. The fuel discharge nozzle is located in the cylinder head  with its outlet directed into the intake port. The nozzle body  contains a drilled central passage with a counterbore at each  end.  [Figure 2-45]  The lower end is used as a chamber for  fuel/air mixing before the spray leaves the nozzle. The upper  bore contains a removable orifice for calibrating the nozzles.  Nozzles are calibrated in several ranges, and all nozzles  furnished for one engine are of the same range and are  identified by a letter stamped on the hex of the nozzle body. Drilled radial holes connect the upper counterbore with the  outside of the nozzle body. These holes enter the counterbore  above the orifice and draw air through a cylindrical screen  fitted over the nozzle body. A shield is press-fitted on the  nozzle body and extends over the greater part of the filter  screen, leaving an opening near the bottom. This provides  both mechanical protection and an abrupt change in the  direction of airflow which keeps dirt and foreign material  out of the nozzle interior. air ratio. A control level is mounted on the mixture control  valve shaft and connected to the cockpit mixture control. The fuel manifold valve contains a fuel inlet, a diaphragm  chamber, and outlet ports for the lines to the individual  nozzles.  [Figure 2-44]  The spring-loaded diaphragm operates  Fuel Manifold Valve Fuel Discharge Nozzle Figure 2-42.  Fuel air control unit. Figure 2-43.  Dual fuel control assembly. 2-28 Fuel inlet filter screen Fuel metering plug Throttle metering shaft Mixture control shaft Fuel inlet from fuel pump To fuel manifold valve Fuel return to fuel pump Intake air Intake air Part throttle position Full throttle position