This article explains how to adjust the Caterpillar 3208 diesel engine fuel ratio control

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NOTE: The same tools are needed for the fuel ratio control adjustment that were used for the fuel setting.
Make reference to Fuel Setting for the tools needed and instructions to install the tools.
NOTE: The fuel setting must be correct before an adjustment is made to the fuel ratio control. Make reference to Fuel Setting.
1. Remove shutoff solenoid (1) and cover (2). Install tools and "zero"dial indicator as shown in Fuel Setting Steps 2 through10. 

2. To check the fuel ratio control setting, move the governor lever slowly to the high idle position. Make a record of the reading on the dial indicator.
Compare the reading with the specification given in the Fuel Setting And Related Information Fiche.

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3. If an adjustment is needed, remove three bolts (3)
from the fuel ratio control. Hold the governor lever in the high idle position and turn flange (4) until the fuel ratia control setting is correct.

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4. Move governor lever to low idle and again move the lever slowly to high idle to check the fuel ratio control setting.

5. Install bolts (3). Flange (4) can be turned a small amount to give alignment for bolts (3).