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Renix distributor rotational play limits?

As Spock once said "when one has tried all the logical explanations, one must consider the illogical ones", LOL. You were dead on sir, the sheer pin failed on mine, big time!!! It finally sheered completely and I could spin the top of the dizzy rotor/assy.

The new one has very little slop or rotational play at all. Changing the dizzy got it running again. But it went back to a back fire like when this all started at 3000 rpm, and shake at idle it did not have before. I eye balled the indexing (cut one ear off so I could rotate it), and the back fire is gone, I got it up to 3800 rpm with no problem. Did not push my luck any higher yet. Now I need to solve the mini shake at idle, which is new. I may cut up a cap and fine tune the location in case I went a 1/16" or 1/32" too far and caused the idle miss. The timing is 15 degrees at idle right now and got up 38 degrees at high rpm per the MT-2500. God I love that tool. I also did one last super sealing job on the MAP sensor vacuum line at the throttle body, as I did not trust that I had an adequate, perfect seal there yet.

I did some thinking on this and with 6 cylinders and 360 degrees, 360/6 = 60 degrees. So if the ECU can advance the spark timing from say 14 degrees to 38 degrees (maybe more) 38 - 14 = 24 degrees of change.

60-24 = 36 degrees of room for error in the Dizzy indexing. Assuming a cap pin to pin diameter of 2-7/8"" (?) I get 9" circumference. 9/360 = .025"/degree

24 degrees.... .025"/degree x 24 degrees = .60" of space between the centers of each cap pin, which is about the length of the rotor tip, maybe less?.

Then with that huge rotor tip, and the gap closed up some by the radius of the two pins in the cap the chances of miss firing go up very fast as the ECU plays with the timing of the spark when you get on the edge where the tip is equidistant from both cap pins. So I can now see the need for precision location of the dizzy, as the ECU has a wide range of degrees (at least 14-38 that I saw today on my MT-2500) to advance the spark limiting any possible slop in the rotor alignment to the cap pin.

But I still have a mystery as to why the last distributor worked for 70,000 miles with out indexing by cutting the ears and rotating the dizzy, as I installed both, and I used the standard tooth guide that leaves the rotor aimed dead on at the #1 pin at TDC. The Cruiser54 method that came from Jeep, has the end of the rotor just barely at the end of the #1 pin at TDC. Which is about 20-30 degrees or so by my estimates.

Perhaps I had the right combination of other defects in mine over the years to get away with it?

One thing most everybody forgets about is that distributor shaft shear pin. It doesn't have to break completely. It can break and the sharp pin ends can kind of catch again fairly solidly, the rotor has moved from initial setup position but you may never know unless you look (check the indexing). The wifes 87 had a CPS issue, something weird happened, one cold morning it flashed back through the TB, maybe ran in reverse a little and blew the check valve cover off the booster. Idled like crap afterwords, I initially thought it had damaged something internally in the engine. On a hunch and having learned on old Dodge and Chevy carburetor motors, where shaft pin breakage was fairly common, I grabbed the rotor and twisted hard, the pin had snapped but caught and jammed again almost solid.

If it isn't something common and normal it is time to start looking at the odd and unusual.
 
this thread is old im aware of that....
I did the reindex on my renix today so i came across this thread and have to wonder if your timing chain stretched necessitating you to reindex your previously installed distributor?
quote ecomike
"But I still have a mystery as to why the last distributor worked for 70,000 miles with out indexing by cutting the ears and rotating the dizzy"
 
well since ive revived this thread im gonna take a pic of where my rotor sits now after cutting the ear off my distributor and reindexing for search purposes.

During my reasearch i have yet to see a pic of where the rotor sits after reindexing...(with a window cut in the cap)
 
Distributor-Index.png
 
My guess would be that the prior one already had a sloppy loose sheer pin, or was corrected in the aftermarket or WTFK? IIRC the one I replaced was labeled Motorcraft? But I thought it was Durajunk buy over 11+ years ago that my ex-ex mechanic from an era long ago put in. Too many moons ago on that...

Or the rig ran so badly for so long as I sorted out the earlier problems from 2003 on (3-4 issues I had to figure out on my own..., that were not covered any where) that I was never able to truly stress the system till this last 18 months? I also changed the plugs about 18 months ago from Bosch platinum that worked great till #1 and #2 started oil fouling. I moved to the slightly hotter NGK plugs cruiser54 was so fond of 5+ years ago. They solved the oil fouling issues (way better than I thought possible), and maybe that was/is affecting spark timing....enough...

I was also seeing low oil pressure as the miss fires let gas built in the 20W50 oil I use, and the gas was thinning the oil. I now have 35-55 PSI year round, instead 18-55 PSI. Small change in plug spark plug timing, and thicker versus thinner oil???? Finding and fixing Uncle Bobs odd throttle adjustment to the throttle body arm? Who knows. All of the above maybe:D

First 10 years I could almost never get it over 2500 rpm...Long story in 15 years of old threads here. The dizzy issue became obvious at high rpms at first only after installing the new one. But if it was the timing chain, it would be an issue now, and is not. I can stomp on the gas in park or drive and gun it to 4500 rpm like a barely broke in engine. 293,xxx miles now.

this thread is old im aware of that....
I did the reindex on my renix today so i came across this thread and have to wonder if your timing chain stretched necessitating you to reindex your previously installed distributor?
quote ecomike
"But I still have a mystery as to why the last distributor worked for 70,000 miles with out indexing by cutting the ears and rotating the dizzy"
 
Oh wow awesome!
thats exactly what i was talking about.
Thanks!

One thing I did learn is that a new Dizzy, and old cam, have almost zero rotational slop!!!

At least on my rig, which tells me from checking two other Renix rigs I have that the sheer pin slop may be a common issue, no one has ever talked about, if there ever even noticed it????

Only reason I know about it, is mine had about 3/8" play out on the end of the rotor (about 20 degrees???), and has zero on the new one and once it sheered it got my attention, LOL as it was 360 degrees :shiver:.
 
all i can say is wow!!!

i highly recommend anyone with a renix that hasnt reindex their distributor to do so asap...

especially with a 5 speed.Believe it or not my transmission always felt notchy but now it shifts like its supposed to.

I guess it had something to do with the synchro speed difference between the input and countershafts due to the motor wanting to lag between shifts?.

Also noticed that after i shift the bucking is completely gone after you let the clutch out.

Truly amazing how much an improperly indexed distributor can affect tranny shifting!!!
 
My transmission is a brand new gearbox from japan with a luk pro gold clutch.

It always felt notchy and i would really pay attention to how i shifted it.

Before doing the dist reindex i was actually looking at getting a hurst shifter and/or taking the tranny apart for new syncros(already running mt90).
But seriously after the reindex its like new!!!
 
The thing that gets me the most is how something so detrimental to performance doesnt have more exposure.

I mean i alaways heard yea do the reindex on cruisers site but didnt really think it was that big a deal.

If there had been more exposure to the symptoms one may have if the dist isnt reindexed i wouldve done it along time ago.

For instance if i knew this had such a detrimental effect on tranny shifting i wouldve put the puzzle pieces together alot sooner.

There seems to be a void somewhere in the symptoms to look for while chasing your tail trying to resolve them concerning the reindex on renix jeeps.

Trust me i spend hours learning things about these jeeps and cant believe the shifting issue never was brought to light to me....always thought it was more of a engine power/performance thing.
 
Off my soap box now and make no mistake i point no fingers in this.
Just know if you have a renix jeep and it shifts notchy and bucks after letting out the clutch CHECK YOU DIST INDEX!
Wonder how many have damned their transmission syncros and it was an index problem all along?
 
As with most of my Tips, they should just be done.
The whole idea is to get the vehicle into shape and eliminate problems you will now never have.

I prioritized them the best I could at the time, but maybe dizzy indexing should be prioritized by you guys and gals. I remember the factory had a hell of a time pinpointing it. We had one customer that drove us nuts with a slight jerking issue. It ended up being indexing of the dizzy.
 
was the customers vehicle a manual trans?
Also can i look foward to any fuel mpg increase now that ive reindexed the dist?
Believe it or not ive owned this 89 XJ since 2001 and was never quite happy with the way it performed until now
Thank you for putting the info out their cruiser!!!
 
It would be more noticeable at low rpm with no torque converter slip, like up shifting a manual to the higher gears or in OD-with a locked TC on an auto.

Folks should also check the rotor for any rotational play on the shaft/gear. My new Distributor has none, zero-nada-none at all, my 89 white 4x4 has almost a 1/4" of slop (have not really gotten it on the road yet, still a work in progress, 3rd spare back up lol) but the one that had the shear pin totally die had a good 3/8" of play days before the shear pin sheared and failed.

Can't help but wonder if the limited early slop (1/4" versus 3/8") hides the Indexing problem some, just before it sheers and goes to back fire-puke madness operation level :D and wakes up the neighbors, LOL

But you are right from what I have seen the last year, it does affect low rpm high gear ignition with no slip in the TC/clutch system.

Off my soap box now and make no mistake i point no fingers in this.
Just know if you have a renix jeep and it shifts notchy and bucks after letting out the clutch CHECK YOU DIST INDEX!
Wonder how many have damned their transmission syncros and it was an index problem all along?
 
Mine has some play in it.

Reading your post about slop and possible sheared pin prompted me to drift out my roll pin just to rule it out and it was one piece intact....guess the slop is from the dist/cam helix gears being worn slightly

I'm of the opinion that once you set the .20 cleareance and the gear is in mesh its good..I'm trying to imagine during operation if the rotor can bounce back and forth even though its driven and in mesh.

One thing i did do as i was rotating the motor for tdc i left the rotor meshed the way it was driven when i set the .20 clearance.
 
I thought I'd add a post to this conversation because this discussion just helped me solve a problem that I've had with my 88 for almost 3 months.

Cruiser said "We had one customer that drove us nuts with a slight jerking issue. It ended up being indexing of the dizzy."

My Jeep had a fishbite type of thing at highway cruising speeds. It took me quite a while just to figure out if it was misfire instead of transmission/torque converter problem. Tested just about everything I could think of and threw more than a few parts at it I'm ashamed to say.

Anyway, the distributor indexing was off. I did Cruiser's tip and she's running great. It's been a long year for me with this thing and I think I finally have it running right. Plenty of stuff to work on still, but it's nice to be done with drivability issues for a while. So Thank You to everyone that contributed here.
 
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