GM Service Manual Online
For 1990-2009 cars only

    Object Number: 320250  Size: SH

    Important: Discoloration of the cap and some whitish build up around the cap terminals is normal. Yellowing of the rotor cap, darkening and some carbon build up under the rotor segment is normal. Replacement of the cap and the rotor is not necessary unless there is a driveability concern.

  1. Inspect the cap for cracks, tiny holes, or carbon tracks between the cap terminal traces. Diagnose the carbon tracks using the following procedure:
  2. 1.1. Remove the engine cover. Turn OFF the ignition.
    1.2. Remove the cap. Refer to Distributor Overhaul
    1.3. Place 1 lead from the DMM on a cap terminal.
    1.4. Use the other lead in order to probe all other terminals and the center carbon ball.
    1.5. Move the base lead to the next terminal. Probe all other leads.
    1.6. Continue this procedure until you test all the secondary terminals.
    1.7. If there are any non-infinite readings, replace the cap.

    Object Number: 301396  Size: SH
  3. Inspect the cap for excess build-up of corrosion on the terminals. Scrape clean the terminals. Replace the cap if the corrosion is excessive. Some buildup is normal
  4. Inspect the rotor segment for excess wear. Replace the rotor if excess looseness in the rotor segment is present.
  5. Inspect the shaft for shaft-to-bushing looseness:
  6. 4.1. Inspect the housing for cracks or damage.
    4.2. If the shaft wobbles, replace the housing assembly.