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Fuel Distributor

The fuel distributor's control plunger, moving up or down in its cylinder, uncovers or covers the metering ports leading to the four metering valves-one for each injector. The metering valves maintain a constant pressure differential for precise control at all fuel flow rates. A cross-section of one metering valve is shown in Fig. 5-4.

Fig. 5-4. Cross-section of one fuel distributor metering valve. Pressure in upper chamber, combined with spring pressure, deflects diaphragm and increases opening to injector.

The fuel distributor is not normally a source of problems. It is, however, a precision device that is easily damaged by plugging or corrosion from contaminated fuel. For fuel filter maintenance information, see LUBRICATION AND MAINTENANCE. On some cars, a mini-filter is installed during manufacture in the fuel inlet bolt at the fuel distributor. This filter should be removed and a normal bolt installed in its place at a specified interval. For more information on identifying and replacing the mini-filter, see LUBRICATION AND MAINTENANCE. Check fuel distributor function by measuring injection quantity, as described in 4.7 Fuel Injectors (CIS, CIS-E, and CIS-E Motronic).

Fig. 5-5 illustrates the fuel distributor's fuel line connections and mounting detail. If either the fuel distributor or the air flow sensor is repaired or replaced, the idle speed and idle mixture (% CO) should be adjusted. See 5.6 Idle Specifications (RPM and % CO). Before making the adjustments, make sure the air flow sensor plate position is correctly adjusted as described above in Air Flow Sensor.

To remove and clean the control plunger, remove the two mounting screws from the top of the fuel distributor and pull the fuel distributor from the air flow sensor assembly. Remove the control plunger and clean it with carburetor cleaner or equivalent. Lubricate the control plunger with a light coat of fuel and reinstall it with the small end facing down toward the air flow sensor plate lever.


Fuel will be expelled when disconnecting fuel unions. Disconnect the battery negative (-) terminal. Do not smoke or work near heaters or other fire hazards. Keep a fire extinguisher handy.


When removing the fuel distributor from the air flow sensor housing, be careful not to let the control plunger fall. If the control plunger is allowed to fall, it may be damaged-rendering the entire fuel distributor unserviceable. The fuel distributor is precision calibrated at the factory and should not be disassembled.


There may be a small spring on the top of the control plunger. Remove the plunger carefully to avoid losing the spring.

Fig. 5-5. CIS fuel distributor mounting and fuel line connections. Torque values shown are for installation.

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