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System Test

  1. Inspect air pump belt. Visually check hoses and tubes for kinks, damage or loose connections. Disconnect air by-pass hose from Air Switching Valve (ASV). See Figure.
  2. With coolant temperature less than 50°F (10°C), start engine and allow to idle. Air should discharge from ASV. When coolant temperature is between 59°F (15°C) and 95°F (35°C), air should stop discharging from ASV.
  3. When air stops discharging from ASV, increase engine speed to 3000 RPM. Air should again start discharging from ASV.


  1. Ensure modulator filter is clean and in good condition prior to performing test. Clean filter with compressed air. Disconnect vacuum hose from EGR valve.
  2. Using a "T" connector, connect a vacuum gauge in EGR valve vacuum line. Ensure engine starts and runs smoothly at idle. This ensures proper seating of EGR valve.
  3. The Vacuum Switching Valve (VSV) and EGR modulator can be checked with engine coolant temperature less than minimum temperature and specified engine RPM in accordance with application. See EGR SPECIFICATIONS  table.
  4. Operate engine with engine coolant temperature less than minimum temperature and specified RPM. No vacuum reading should be obtained when operated with engine coolant temperature less than minimum temperature.
  5. Operate engine at normal operating temperature and specified RPM. See EGR SPECIFICATIONS  table. A low vacuum reading should be obtained.
  6. Disconnect hose from the "R" port of EGR vacuum modulator. See Figure.
  7. Using additional hose, connect "R" port directly to intake manifold. High vacuum reading should be obtained at specified engine RPM. See EGR SPECIFICATIONS  table.
    NOTE: Engine should misfire due to large amounts of exhaust gas being injected into intake manifold.
  8. To check EGR valve, apply vacuum directly to EGR valve with engine idling. Engine should run rough or stall. If system did not operate as described, each component should be tested.
EGR SPECIFICATIONS

Model Type Minimum Temperature Engine RPM
Land Cruiser 127°F (53°C) 2500
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