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Home >> Mercedes Benz >> 1988 >> 420SEL >> Repair and Diagnosis >> Engine Performance >> System >> EGR System >> Diesel System Testing >> Vacuum Amplifier
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Vacuum Amplifier

  1. Connect vacuum tester with "Y" fitting to connection "A" and read vacuum value at idle speed. For manual transmissions, it should be about 9 in. Hg. For automatic transmissions, it should be about 10 in. Hg.
  2. If vacuum is greater or below specified value, adjust vacuum. To adjust vacuum, pull off dust cap from vacuum amplifier and turn adjusting screw with a 4 mm socket wrench until specified value is obtained. If vacuum value is not okay, go to next step.
  3. Check supply vacuum at connection. Replace vacuum amplifier if necessary. Check vacuum lines.