jamespwsullivan Posted October 5, 2022 Share Posted October 5, 2022 Here is a picture of the rotor location when #1 is at TDC. Reading Cruiser54's tip I think that the rotor tip is in fact slightly trailing the #1 location. I'm just looking for some feedback or confirmation. thoughts? Link to comment Share on other sites More sharing options...
Ωhm Posted October 5, 2022 Share Posted October 5, 2022 19 minutes ago, jamespwsullivan said: thoughts? My indexing guess is one tooth off. Move rotor tip clockwise. Link to comment Share on other sites More sharing options...
DirtyComanche Posted October 5, 2022 Share Posted October 5, 2022 17 minutes ago, Ωhm said: My indexing guess is one tooth off. Move rotor tip clockwise. Is a 20 thou gap what's called for? OP's is wrong for sure though. Off a tooth maybe, or he needs to mod it so he can spin it to the right place. Link to comment Share on other sites More sharing options...
Ωhm Posted October 5, 2022 Share Posted October 5, 2022 18 minutes ago, DirtyComanche said: Is a 20 thou gap what's called for? Don't recall where that photo came from, but I do recall that the rotor tip needs to be pass the distributor tower (#1). Keep in mind that the 20thou gap is fixed. Meaning when the gears (distributor/cam) are engaged, the rotor tip will/should end up at that location. It's no easy task to line this up and drop it down. Link to comment Share on other sites More sharing options...
DirtyComanche Posted October 5, 2022 Share Posted October 5, 2022 1 minute ago, Ωhm said: Don't recall where that photo came from, but I do recall that the rotor tip needs to be pass the distributor tower (#1). Keep in mind that the 20thou gap is fixed. Meaning when the gears (distributor/cam) are engaged, the rotor tip will/should end up at that location. It's not fixed if you've cut the locating tab off the distributor. Link to comment Share on other sites More sharing options...
Ωhm Posted October 5, 2022 Share Posted October 5, 2022 2 minutes ago, DirtyComanche said: It's not fixed if you've cut the locating tab off the distributor. True, but that's not me. Link to comment Share on other sites More sharing options...
DirtyComanche Posted October 6, 2022 Share Posted October 6, 2022 1 hour ago, Ωhm said: True, but that's not me. My XJ came that way. Not because they were trying to make anything better, but because they put the distributor so that the #5 post was hooked to #1 spark plug. Link to comment Share on other sites More sharing options...
jamespwsullivan Posted October 6, 2022 Author Share Posted October 6, 2022 So if I do the indexing procedure described by Cruiser54, I can adjust it that way rather than lifting up the dizzy and dropping it back down one tooth later? If I am seeing the drawing right, it's very helpful. The rotor tip must be completely past the #1 post. Link to comment Share on other sites More sharing options...
DirtyComanche Posted October 6, 2022 Share Posted October 6, 2022 5 minutes ago, jamespwsullivan said: So if I do the indexing procedure described by Cruiser54, I can adjust it that way rather than lifting up the dizzy and dropping it back down one tooth later? If I am seeing the drawing right, it's very helpful. The rotor tip must be completely past the #1 post. Maybe. You still want the rotor in the right place or the disty winds up rotated to a potentially undesirable location. In the case of my XJ #1 and #6 plug wire were too short because of what they had done, but you could get it to go together, so I left it alone until other issues forced me to address it. I wish I had simply fixed it when I first got the stupid thing. Link to comment Share on other sites More sharing options...
cruiser54 Posted October 6, 2022 Share Posted October 6, 2022 Many diagrams are off. Use this one to get the dizzy close to correct and then make your adjustment after cutting the tab. Link to comment Share on other sites More sharing options...
Ωhm Posted October 6, 2022 Share Posted October 6, 2022 Purpose of the tabs on the distributor housing is for keeping the SYNC SIG pickup and the distributor cap in their correct locations. Rotating the distributor housing, this way or that way, one could possibly shift INJ firing order. Not change the firing order but shifting it. If INJ#1 calls for fuel, INJ#5 or INJ#4 could be fired, depending on which way the distributor housing was turned. Link to comment Share on other sites More sharing options...
jamespwsullivan Posted October 6, 2022 Author Share Posted October 6, 2022 @Ohm I think I understand that, the pic I posted wasn't oriented well enough for all to see that my cap, rotor, etc. is very close to what Cruiser's picture shows. Looking at the number of teeth on the distributor shaft I suspect that a full tooth would be too much change. That's why I'm suggesting that I tweak the position after cutting off the tab. Am I missing something you're telling me? And BTW, why is it that MJs got shipped from the factory with the distributor (incorrectly located? Does it have to do with the location of the tab on the distributor? Is it the location/nub that the tab locks into? Thanks to all who have contributed so far. I'll keep this updated with status. Link to comment Share on other sites More sharing options...
Ωhm Posted October 6, 2022 Share Posted October 6, 2022 2 hours ago, jamespwsullivan said: And BTW, why is it that MJs got shipped from the factory with the distributor (incorrectly located? Does it have to do with the location of the tab on the distributor? Is it the location/nub that the tab locks into? IIRC, distributors itself were indexed incorrectly. Meaning distributor gear to rotor tip was wrong. This faulty distributor made its way into production vehicles. I believe notice was sent to all owners for replacement distributors. Remedy was to replace with corrected distributor. Till then, one could cut the tab and fix it that way. So, if the swing of the distributor housing is minimal, you’ll be OK, if not, you may shift the INJ’s firing. This problem showed up as ‘crossfire’ in the cap at higher RPMs with full advance on timing. Link to comment Share on other sites More sharing options...
cruiser54 Posted October 6, 2022 Share Posted October 6, 2022 No notice was sent. There was a TSB on it though. Remedy was to index the dizzy, not replace. 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. Link to comment Share on other sites More sharing options...
jamespwsullivan Posted October 10, 2022 Author Share Posted October 10, 2022 Results of our science experiment. Full disclosure--both of my parents were teachers so my brother and I are all about one step at a time, and we are also about getting to the bottom of something so that we understand it. So, don't take this as any distrust of anything that people contributed. i love it when things work out. Picture #1 is another shot of the original distributor with a cut off cap and #1 at TDC. Sorry the shot isn't lined up so it's easy to see the line of the side of the cylinder head. Next picture is the new distributor (NAPA NND ST4692) installed. Engine is still #1 at TDC. So, we didn't measure the gap to get the .020" shown in the earlier diagram, but the new distributor installation sure looks a lot more like that diagram - which confirms (probably for the umpteenth time) that the original distributor in the vehicle was not manufactured properly and needed to be indexed. Working on the rear brakes right now so I can't do a test drive, but I'm optimistic that this change may have an impact on the smoothness of acceleration under load. Link to comment Share on other sites More sharing options...
cruiser54 Posted October 11, 2022 Share Posted October 11, 2022 It's better, but I would want to see it from the side. Link to comment Share on other sites More sharing options...
Ωhm Posted October 11, 2022 Share Posted October 11, 2022 On 10/10/2022 at 2:12 PM, jamespwsullivan said: original distributor in the vehicle was not manufactured properly and needed to be indexed Perfect example. Link to comment Share on other sites More sharing options...
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