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System Test

  1. Check hoses for proper routing and condition. Cold start engine and run at idle. Watch secondary EGR valve and be sure it does not operate as engine speed is increased to 2500 RPM. If it does, test thermo valve as follows:
  2. Detach Green striped hose from thermo valve. Connect hand vacuum pump and apply vacuum. If no vacuum is available through thermo valve, valve is okay. Reconnect hose.
  3. Warm engine to normal operating temperature. Increase engine speed to 2500 RPM. Secondary EGR valve should now be operating. If not, check EGR and thermo valve and replace as necessary.
  4. Check operation of sub EGR valve by manually pulling linkage to be sure it moves smoothly. If hard to move, remove sub EGR valve and check for carbon deposits. Clean or replace valve, as required.
  5. Detach Green striped hose from carburetor nipple and attach vacuum pump to hose. Manually pull on linkage of sub EGR valve, and at same time apply 6 in. Hg to vacuum hose. If idle becomes rough, EGR system is okay. If idle does not change, main EGR valve is improperly operating and must be replaced.
NOTE: If difficult to remove sub EGR valve, spray with suitable solvent (such as for manifold heat valves), after removing rubber boot. Let soak, then remove valve.
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