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Servo Vacuum Test

  1. Disconnect linkage, bead chain or cable from servo to throttle. Make sure electrical connector to servo is still disconnected. Start engine and let idle. Manually actuate servo vent and vacuum control valves by connecting jumper wires from battery positive post to pins "A" and "E" on servo assembly.
  2. Connect another jumper wire between pin "C" of servo and ground. With brake and clutch pedal (M/T) in free position, servo should fully pull in. If servo fails to pull in, go to step 5).
  3. If servo pulls in, remove jumper wire from pin "E" on servo. Servo should stay in position. If servo stays in position, check connection of electrical connector at servo. If servo fails to remain in position, remove larger of two hoses and plug orifice of servo.
  4. Reconnect jumper wire to pin "E" until servo fully pulls in, then remove jumper wire. If servo fails to stay in position, replace servo. If servo stays in position, check brake and/or clutch release valve for adjustment. Check hoses and valves for leaks, and repair or replace as necessary. Check for proper system operation.
  5. Remove larger of two hoses and plug orifice of servo. Servo should pull in. If servo fails to pull in, remove smaller hose from servo and check for vacuum. If vacuum is present, inspect connectors for leaks. If okay, replace servo.
  6. If no vacuum is present, check connectors between servo and vacuum source. Repair or replace as necessary. If servo pulls in, check brake and/or clutch release valve for adjustment. Check hoses and valves for leaks, repair or replace as necessary.
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