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Home >> Nissan-Datsun >> 1981 >> Cab & Chassis >> Repair and Diagnosis >> Engine Performance >> Engine Control Systems >> Intake Manifold Vacuum Control System >> Testing & Adjusting >> Boost Control Unit >> Checking Boost Control Unit Operating Pressure
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Checking Boost Control Unit Operating Pressure

  1. To check pressure, engine should be at normal operating temperature, idle speed set to specifications and transmission in neutral. Connect a tachometer to engine and a vacuum gauge to intake manifold.
  2. Run engine under no load and note vacuum reading. Increase engine speed to 1500-2000 RPM, then quickly close the throttle. Manifold vacuum should increase to 23.6 in. Hg or more and then gradually decrease to level noted at idle.
    Boost Control Unit Operating Pressures (At Sea Level)

    Application Pressure (In. Hg)
    510
      Man. Trans. 22.8-24.4
      Auto. Trans. 21.3-22.8
    Pickup 22.8-24.4
  3. If boost control unit operating pressure at idle is not as specified in "Boost Control Unit Operating Pressures" table, proceed as follows:
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