Distributor Indexing

Firing Order

Renix dizzy indexing

  1. Remove the distributor cap and cut a “window” into the side of the distributor cap at the #1 spark plug wire post . The “window” should be large enough to allow easy visual inspection of the position of the distributor rotor at the #1 spark plug wire post. Reinstall the distributor cap.
  2. Install a ¾” wrench or socket onto the vibration damper retaining bolt. Rotate the engine in a clockwise direction until the #1 cylinder is at top dead center. Align the timing mark on the vibration damper with the “0” degree mark on the front cover timing scale. The tip of the distributor rotor should be near the #1 spark plug wire post.
  3. Disconnect the distributor electrical connection. Remove the distributor holddown clamp, holddown bolt and distributor. Remove the distributor cap and rotor.
  4. Place the distributor housing upside down in a soft jaw vise. Scribe a line 1/2 inch from the end of the distributor locating tab. Cut the distributor locating tab at the scribed line with a saw.
  5. Remove any burrs and metal filings from the distributor. Reinstall rotor.
  6. If necessary, using a flat blade screwdriver, turn the oil pump gear drive shaft until the slot is slightly past the 11 o’clock position. The oil pump gear drive shaft is accessible through the distributor mounting bore in the engine block. A little tip here. Rather than use a dizzy gasket, use an o ring instead. NAPA #727-2024.Dizzy o ring
  7. Visually align the modified locating tab area of the distributor housing with the holddown clamp bolt hole.
  8. Turn the rotor to the 4 o’clock position.Dizzy tab cuts
  9. Lower the distributor into the engine block until it seats. The rotor should now be very close to the 5 o’clock position.
  10. Reinstall the distributor cap with the cutout “window”. Rotate the distributor housing until the trailing edge of the distributor rotor tip is just departing from the #1 spark plug wire post terminal .
  11. Reinstall the distributor holddown clamp and bolt.. Reinspect the position of the rotor to the #1 spark plug wire post to insure that it has not moved.
  12. Install the new distributor cap, reconnect the distributor electrical connections.

Here’s WHY distributor indexing is so important:

Distributor indexing explained
For clarification though, that’s not a cam sensor inside the Renix dizzy. It’s there to fire the injectors sequentially with the firing order. You’ll never notice if it went bad because the ECU will try to “guess” where it is and does a heck of a job at it.

As for the “timing”, it is controlled by the ECU. Ever notice how wide the tip of the rotor is? Try and wrap your head around this:

When the ECU yells “Fire” to the ignition control module, where is the rotor in relationship to the dizzy terminal? Not to the terminal yet? Past the terminal too far?

What happens to the spark/secondary ignition strength when it has to jump the Grand Canyon in comparison to shooting from a rotor tip?

Tip 13 gets the thing right. Use Tip 12 first to guarantee you’re on #1 TDC.

Revised 11-19-16


10 thoughts on “Distributor Indexing”

  1. Hi.

    Thank you for all the great information. I am curious about the rotor position. You indicate is at TDC it should be at the trailing edge of the rotor should be at the #1 post. However, the Haynes manual states that it should be the leading edge. Why the discrepancy??

    1. As usual Haynes is wrong about that, just as they are about spark plug wire placement on the distributor cap.

      The info I provided is directly from a Jeep Technical Service Bulletin and is proven to work.

  2. I changed my 89 xj 4.0 to this firing order and now it wont even crank. Why would this be? is my firing order different?

  3. When you reference the 4 o’clock position, where is 12 o’clock? This is facing the distributor from the passenger side fender with the #1 cylinder on your right?

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