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Belt-Driven Pumps

  1. Remove vacuum hose from inlet port and plug opening. Install vacuum gauge to inlet port. Block drive wheels, apply parking brake, and place auto. trans. in "PARK" or man. trans. in "NEUTRAL".
  2. Start engine and operate at idle while watching vacuum gauge. After 30 seconds, gauge should read 21 in. Hg; if not, check for vacuum leaks, drive belt tension, and idle RPM before replacing vacuum pump.
    Fig 1: Belt-Driven Pump Test Connections Step 3) uses this connection. Steps 1) and 2) connect gauge directly to inlet port.
    G13880
    NOTE: For problems of excessive brake pedal effort, or if the brake warning light is "ON", check for vacuum leaks, drive belt tension or idle RPM.
  3. Reconnect outlet hose (if removed). Connect inlet hose. Place vacuum gauge with a "T" fitting in inlet hose between pump and accessories. See Fig 1 . With engine idling, wait one minute and check vacuum. If reading is not less than 18 in. Hg, pump is okay and fault is not with vacuum system.
  4. If vacuum is still low, check all attaching hoses for leaks. If still low, check all vacuum operated accessories for leaks or bad connections and repair or replace as required.
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