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System Test

  1. Check hoses for proper routing and condition. Cold start engine and run at idle. Watch sub EGR valve and be sure it does not operate as engine speed is increased to 2500 RPM. If it does, replace thermo valve.
  2. Allow engine to warm to normal operating temperature. Repeat increase of engine speed to 2500 RPM. Sub EGR valve should now be operating. If it does not, check EGR valve or thermo valve and replace as necessary.
  3. Detach green stripe hose from thermo valve. Connect hand vacuum pump and apply vacuum. If no vacuum is available through thermo valve, it is okay. Reconnect hose.
  4. Detach green stripe 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, sub EGR valve is okay. If idle does not change, main EGR valve is improperly operating and must be replaced.
  5. Check operation 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.
    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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