Renix Distributor Indexing - JeepForum.com
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post #1 of 6 Old 08-05-2020, 02:41 PM Thread Starter
Saudade
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Renix Distributor Indexing

Back in June I changed out my distributor in my '88 XJ. I noted that the mounting tab had been cut off. I thought this was odd but Cruiser54 pointed out there was a TSB (#18-53-88) regarding this due to an ignition crossover that might cause bucking or surging. While I never experienced this, I felt I needed to do this the proper way.

So I chopped up my old cap to cut a window.



Then set the engine to top dead center.



Verified the rotor pointed at #1



Then installed the "cutaway" cap. You can see the end of the rotor tip at the extreme left side of the window (Should've cut the window larger). I was about 5/16" away from the post.




So out came the distributor and made the mark to cut.



Used my dremel with a cutoff wheel to whack the tab off. Cleaned up the edges with some 220.



Reinstalled the distributor and clamp. Clamp tightened down to just snug but could still rotate. Turned the distributor until the rotor barely past the post. (The TSB says .020" but I eyeballed it). Sorry I guess I forgot to take this pic.

Tightened down the clamp, reinstalled the good cap, cranked the engine and GLORY, it started. Started it several times to make sure I still didn't find some way to mess this up.

Here's the "trophy" I have to mark the occasion.



So once again thanks to Cruiser54

Cruiser54's tip can be found here.
http://cruiser54.com/?p=68

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post #2 of 6 Old 08-05-2020, 03:41 PM
RedBolide
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Very interesting, thanks for posting the pics. I'm about to tackle some work on my Renix so it's nice to keep this in mind.

'03 Wrangler Sport / '98 Grand Cherokee Laredo / '90 Comanche Eliminator
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post #3 of 6 Old 08-06-2020, 07:11 AM
cruiser54
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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.

If you own a Renix Jeep, you must check this out:


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post #4 of 6 Old 08-06-2020, 10:28 PM
chromegrille
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And...if you had ever driven a vehicle that was bucking like a bronco because of this condition, you'd swear that there was something wrong with the engine, transmission or some other major component. Drove us crazy on the very first one we encountered.
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post #5 of 6 Old 08-07-2020, 05:44 AM
cruiser54
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Quote:
Originally Posted by chromegrille View Post
And...if you had ever driven a vehicle that was bucking like a bronco because of this condition, you'd swear that there was something wrong with the engine, transmission or some other major component. Drove us crazy on the very first one we encountered.

Same here!! Brand new 88 XJ and the guy was from another town.

It's just one of those things you check. And it's almost always off.

If you own a Renix Jeep, you must check this out:


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post #6 of 6 Old 08-07-2020, 09:05 AM Thread Starter
Saudade
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I drove mine for about 5 weeks with the unmodified distributor. I didn't drive a lot of miles since everyplace is a short trip, but did lot's of starts. Didn't have any issues. So I'm thinking, what's the big deal? Sure, some may do it but mine is fine. Nevertheless, it kinda nagged at me. It's a quick fix too so why not make it right.

Honestly, I was quite surprised at how far off the rotor was. I realize the spark event is over by the time the engine reaches TDC but it made me wonder where's the rotor in relation to the post at idle and full advance.

Anyway, I opened the window on the old distributor out to the adjacent posts so I can see the entire view next time.
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