Mercedes Coupes/Sedans/Wagons 1974-1984 Repair Guide

Carburetors

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ADJUSTMENTS



Stromberg 175 CDT

See Figure 1

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Fig. Fig. 1: Carburetor applications chart

  1. Turn off the heater and A/C and run the vehicle to normal operating temperature.
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  3. Check the throttle valve for ease of operation.
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  5. Connect a tachometer. Adjust the idle speed to specifications with the idle speed adjusting screw.
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  7. See whether the idle speed stop is resting against the throttle valve lever and not against the vacuum governor. Set the vacuum governor back if required.
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  9. If an exhaust gas analyzer (CO meter) is available, check the exhaust gas for percentage of Carbon monoxide (CO). On 1975-76 models, check CO without air injection. Disconnect and plug the centerline from the blue switch-over valve. On 1977 models, be sure the wheel for altitude compensation is set properly.
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  11. Remove the plug in the exhaust gas tapping pipe and connect a tester to the hose.
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  13. If required, adjust the CO by means of the adjusting screw. Loosen the locknut while simultaneously holding the nozzle screw and turning the fuel shutoff valve. Accelerate a brief instant after each adjustment of the idle speed and fuel control screw to stabilize the mixture.
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  15. Check the idle speed again and adjust with the idle speed adjusting screw, if required.
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  17. Adjust the control linkage as follows:
    1. On vehicles with a manual transmission, attach the control rod and adjust it so that the roller rests in the gate lever without binding. The control lever is equipped with right and left-hand threads.
    2.  
    3. On vehicles with an automatic transmission, run the engine at idle speed. Set the control rod so that it can be attached with no binding.
    4.  

  18.  

Solex 4A 1

  1. The idle speed adjustment on this carburetor is made with the air cleaner installed and the crankcase breather connected.
  2.  
  3. Warm the engine to normal operating temperature. Do not adjust the idle after the engine has been driven very far or the engine will be too hot.
  4.  
  5. Check the throttle valve shaft for binding.
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  7. Adjust the idle speed to specifications with the idle speed adjusting screw. This should be done with a tachometer installed. Be sure that the idle speed stop is on the throttle valve lever and not on the vacuum governor. Loosen the spring of the vacuum governor, if necessary, by altering the setting of the adjusting nut.
  8.  
  9. If a CO meter is available, check the Carbon monoxide (CO) content of the exhaust gas without air injection. To cancel air injection, disconnect the red vacuum line (1974) or blue-violet line (1975-76). Follow the manufacturer's directions for use. If necessary, turn both mixture control screws to the right against the stop. Turn both screws simultaneously to the left until the CO percentage is within specifications. Turning the screws out will give a richer mixture and turning the screws in will give a leaner mixture.
  10.  
  11. Check the idle speed again until both the idle speed and CO percentage of the exhaust gas are as specified.
  12.  

 
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