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Home›Repair guides›2. Set the carburetor power mixture adjustment valve at

Cummins — 2. Set the carburetor power mixture adjustment valve at

For these Cummins models: G-1710, G-495, G-743, G-855, GTA-1710, GTA-743, GTA-855.

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Procedure

  1. 3. Close the idle adjustment; then open two and one-half © turns.
  2. 4. Remove the pipe plug and attach a pressure gauge (water manometer) between the main line pressure regulator and the “Thermac” pressure reduction valve. Also remove the pipe plug and attach a pressure gauge (water manometer) on the “Thermac” pressure reduction valve, or Y% pipe plugs on thermac in and out.
  3. 5. Remove the pipe plug from teh intake manifold and - install a vacuum gauge or mercury manometer.
  4. 6. Open the main line gas supply valve.
  5. 7. Adjust the line gas pressure to the “Thermac” pressure reduction valve to 10 inches (254 mm) of water.
  6. 8. Start the engine, using normal starting procedure. a. Remove the cap from the “Thermac” pressure reduction valve. b. Insert screw driver in adjusting screw, and adjust to obtain desired pressure, 3 to 6 in. on water manometer, replace cap. ©
  7. 9. After the engine coolant aitains operating temperature (140-160°F) operate the engine at the rated RPM and system load. a. With the engine operating at system load and speed check the gas pressure to the "Thermac” pressure reduction valve. If this differs considerably from the pressure as set in step 7 above: 1) the main line pres- sure regulator is faulty; 2) the main line is undersized; 3) the orifice is incorrect for main line pressure, see drawing on page 10. Any of the above three steps, or all three could cause faulty gas pressure. Consult the Any and all final adjustments on the engine should be made to obtain the highest amount of manifold vacuum, or lowest boost. Any adjustment that causes increased boost or less vacuum, is an incorrect adjustment. Final adjustments must be made with the engine operating at its rated load and speed.

Source: manual:CUMMINS G495 G743 G855 GTA743A GTA743B GTA855 G1710 GTA1710 Operation and Maintenance Manual (2).pdf. Figures and steps are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.