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. Use Tip 12 first to guarantee you’re on #1 TDC.
  3. 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.
  4. Disconnect the distributor electrical connection. Remove the distributor holddown clamp, holddown bolt and distributor. Remove the distributor cap and rotor.
  5. 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.
  6. Remove any burrs and metal filings from the distributor. Reinstall rotor.
  7. 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
  8. Visually align the modified locating tab area of the distributor housing with the holddown clamp bolt hole.
  9. Turn the rotor to the 4 o’clock position.Dizzy tab cuts
  10. Lower the distributor into the engine block until it seats. The rotor should now be very close to the 5 o’clock position.
  11. 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 .
  12. 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.
  13. 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? Poor ignition performance, bucking, jerking, longer crank times.

The factory was aware of this and issued a Technical Service Bulletin on it. This Tip, #13, is a condensed version of that factory TSB. You wouldn’t believe how many we found out of whack when I worked at the dealership. Yours is probably messed up also. RARELY did we find one set accurately.

Use Tip 12 first to guarantee you’re on #1 TDC.

Revised 08-19-19

 

45 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?

  4. Why did Jeep put out a technical Service bulletin on distributor indexing? Was there a recall or another reason as to why the distributor needed re-indexing?

    thanks in advance

    1. They did it because there were some driveability issues with light throttle bucking.

      This explains why. It’s at the bottom of the distributor indexing tip.

      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?

      Use Tip 12 first to guarantee you’re on #1 TDC.

  5. I’ve been working through all the steps and have come to this, when indexing the distributor once I have set top dead center the rotor button has about 10 degrees of play in rotation. Brand new distributor, should I take up the slack in clockwise rotation to set it or is this unusual?

    1. I discovered the real roll pin securing the gear on the distributor was split into multiple pieces. So I replace the distributor cleaned out the oil pan new oil pan gasket yesterday. Still … Starts to miss back fire and lose power after worming up while driving. Wold the tube headers be heating the intake or injectors up any more than normal? Still scratching my head. Going to go back and check all the new sensors for any bad out of the box ones.

  6. You indexed the distributor again, right?

    I wonder if you’re having a fuel delivery issue. Ever checked fuel pressure at the rail?

    Don’t worry about the headers causing too much heat.

    1. I checked and discovered the intake manifold bolts were not really tight. One of the bolts on the bottom is missing the factory washer and has a three-quarter inch lock washer underneath a flat washer on it. I keep finding stuff like this that the machine shop I had rebuild the engine did. One TPS bolt was broken off. MAP vac line was plugged off and laying on the intake. Three of the spark plugs were missing the seal washers on them. Missing bolts on the engine being replaced by longer bolts with a stack of washers to make up the difference. Etc. So with that in mind, same mechanic told me the fuel pressure was 50 psi and that the old one was blowing air bubbles through it when he disconnected it from the rail and turn it on. in spite of the headache I’m getting a very good education on the my Jeep. Thank you by the way for me and so many others.

    1. Thank you for all of your help. Yes I’m going to go back through everything and check behind him and myself. Tightening the intake exhaust manifold bolts didn’t change anything so I will look into the fuel delivery system. Kind of makes me wonder how he said there was air bubbles coming out with the fuel. He installed a new fuel pump but I think I might go and recheck that. Also the fuel pressure.

  7. i have 89 cheroke with a 98 grand cherokee motor. it had a cracked flex plate. put in nw one and now will only idle, will not excelerate, checked every thing could think of on the list, new fuel pump all vacum connects inj, tps only thing diff is flex plate. took it back out window off by 1/2 in. have ordered in several none match up will newer style with more solid ring work? what am i missing this is 3rd time taking apart, almost mor fun than i need. at 67 yrs old. thanks would sure apreciate ideas. love the site have learned a lot just not enough.

  8. from my understanding of this TSB, we are essentially cutting the locating tab off in order to fine tune the alignment of the cap and rotor correct?

  9. Hey Cruiser, I’m hoping you can help with this. It’s a renix stroker with an REM and wideband o2. I don’t remember my knock and ign adv from before the stroker, but since it I’ve noticed my ign adv is very high under light throttle and cruising on the highway. Under load/acceleration, it drops back. With light throttle or cruising, it stays between 39 to 45 adv, with load/acceleration it drops back into the 20’s and early 30’s. Knock sensor is reading 0 at idle but goes up to 50’s under load, stays in the 15 to 30 range with light throttle. It starts well and runs good. I’ve indexed the distributor exactly how you show it and it works but feels like it should have more power up top. Would moving the distributor 1 tooth forward and keeping the rotor just departing the #1 cylinder like you show to do, change or effect anything? Engine specs are 68-232-4 comp cam, scat rods, scat crank, balanced everything, racetec 18cc dished pistons, bored .060, ls1 valves & springs, 7120 head ported dished polished, banks header, bosch 4 hole injectors, rollmaster double roller, 1.6 ratio harland sharp roller rockers, 62mm bbk throttle body, 99+ intake, thor cowl intake, wideband o2 piggybacked through REM, REM also running 3 fans, and a flowmaster 40 series. Sorry for the long post for a question and thanks.

    1. Sounds like the knock sensor is doing it’s job. Indexing the distributor is all you want to do in that department.

      How many miles are on this engine? Tire size and gearing?

      1. 365 miles on the stroker. Stock 3.55 gears and stock tire size. I ended up having a small hole in the intake valve that was letting coolant into cylinder 1 and causing a misfire and running bad. Waiting on another head currently.

  10. Do 12 and 13 have to be done together, or could I only do 12 for now? 13 seems pretty intense. The point of this tip is to get stronger spark by increasing the distance it has to jump? And to fine tune the timing to a post-production spec that was deemed better? Sorry I just can’t quite wrap my head around this one, I think it may be beyond my understanding/experience, but I want to do every tip I can, especially if they are critical!

  11. from the 2nd part of Tip 13:

    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?

  12. Yeah that’s the part I don’t understand, just a lack of knowledge on my part. You are aligning the distributor rotor to be in sequence with the adjustment to #1 TDC you would have just made? Could you explain the purpose of cutting 1/2″ off the tab?

  13. Yes, to obtain correct alignment. The dizzys were not adjustable from the factory and many were not indexed correctly to maximize the spark from rotor to cap. In order to index the dizzy, the locating tab needed to be removed so the housing could rotate in order to get the proper indexing.

  14. Ah, I finally understand! Is there a major difference after completing these tips, or as someone who has just grasped the concept of this, should I just leave well enough alone and let the computer continue guessing?

  15. You’re right, I should enjoy my Jeep this summer, not just work on it! I will check it before I do anything, but I’ll do that later!

  16. I have a 1989 Cherokee, we’ve been chasing a mid range miss. We indexed the distributor and fixed the stumble but I have a new issue. The flex plate is cracked. I have an aftermarket flex plate but the tone ring is indexed about an inch different than the factory one. Will this affect the performance or will the crank sensor and ecu compensate for the difference? We are in a time crunch and needing the jeep otherwise I wouldn’t even consider it.

    1. First off Nathan, let me apologize for the late response!! WordPress goes along and alerts me on a regular basis of these posts,and then sometimes saves them up for a while. ARGGGHHH!
      Anyway, don’t use the flexplate. Get a used one.

  17. Hey Cruiser, revisiting this one because my distributor seal is leaking oil, so I’m considering doing this tip since I have to remove the distributor anyway. How would I check the current indexing, by doing tip 12 and then mark the location of #1 terminal, remove the distributor cap and see if the rotor tip is at or near #1? just don’t wanna do anything if I don’t have to, so thought I should check first before doing the tip. Even if I don’t end up doing tip 13, would you still recommend using an O ring instead of dizzy gasket to fix the oil leak? Thanks in advance!

  18. Use Tip 12 to find top dead center on #1 per the instructions. Then do Tip 13 using an old distributor cap cut up. Yes, use an o-ring as a seal.

  19. Okay, I guess I will just do it. I was gonna cheap out and try to just check it without having to get a new cap, but it’s probably not indexed right, so I’ll just commit. Does the distributor fire clockwise or counter clockwise? just so I know which is the trailing edge of the rotor.

  20. firing order is on the intake manifold.
    If you look at the cap and where the plug wires go, you’ll see the rotation. Also, the photo in Tip 13 is a clue.

    1. I did this today my 89 jeep would buck spit and sputter like crazy @ 2000 rpms this fixed it 100% thanks very much brother I really appreciate your wisdom cruiser54.

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