HOrnbrod Posted January 24, 2013 Share Posted January 24, 2013 I'm replacing my original distributor with a new 94-99 unit because I'm getting a code 54 (Distributor sync pickup - Change sync sensor in distributor), which I'm hoping is the cause of the random engine shutdown I'm getting while driving. It was just a few $$ more than the sync pickup for the original distributor, so I figured I'd just get a whole new distributor. Also to replace the sync pickup on the old 91-93 unit, you have to pull it and completely disassemble it including the drive gear in order to replace the sync pickup. On the 94-99 unit you can change the pickup w/o pulling the dizzy - mo betta. Anyhow, I haven't changed a distributor in awhile and was reading over some how-to's to refresh. Everyone of them said rotate the engine to TDC on the compression stroke, mark the distributor body and rotor position, blah, blah. In the past all I did was mark the distributor shell, mark the rotor position, then install the new distributor back in the same way. The rotor only goes on one way, and the shell has to do the same for the alignment clamp bolt hole. So is it necessary to do it at TDC if I don't turn over the engine while changing the dizzy out? If so, why? I like doing things the easy way. Link to comment Share on other sites More sharing options...
ComancheKid45 Posted January 24, 2013 Share Posted January 24, 2013 I really don't have a straight answer but finding TDC is very simple on our engines ;) Id just do it to be sure the 1st time Link to comment Share on other sites More sharing options...
Biotex Posted January 24, 2013 Share Posted January 24, 2013 You can do it the easy way sure. Basically the crank turn twice for every one revolution of the rotor. Therefor if you had it in 180° out, the rotor would be pointing in the opposide direction. The reason I always put the engine in TDC compression is just so I don't have to mark everything. I set TDC, then just yank everything out. To me, that is the easy way with no second guessing, but not really the easy way for you it sounds. To be clear and answer your question, yes you can mark the rotor to the housing, and the housing to the block and achieve the same result. Link to comment Share on other sites More sharing options...
jimoshel Posted January 24, 2013 Share Posted January 24, 2013 I always just mark the rotor and pull. I think the main reason for finding TDC is in case the engine gets moved before installing the Dizzy. Link to comment Share on other sites More sharing options...
HOrnbrod Posted January 25, 2013 Author Share Posted January 25, 2013 I always just mark the rotor and pull. I think the main reason for finding TDC is in case the engine gets moved before installing the Dizzy. Exactly. The easy way. There's no need I can see for the TDC compression set on the Mopar dizzy. If the rotor is pointing exactly as when pulled, it's right. There's no 180* out possibility like there was on some of the old GM distributors. Link to comment Share on other sites More sharing options...
gogmorgo Posted January 25, 2013 Share Posted January 25, 2013 I once pulled a dizzy on a Chevy 305, to replace the pickup coil (same thing, pull the drive gear off and all) and somehow when I put it back together, there was no feasible way to put it back in exactly as it was marked. I had turned it to tdc, and I know it could go in either the way it came out or 180° from that, but it would only seat at 45° out of where my marks were... It fired up like that, and I got a mechanic to throw a timing light on it, and it was right where it should be... I would swear to you that tdc moved. As far as finding where tdc is first, no it doesn't matter much, but it can be helpful if things might move while you've got the dizzy out. Or so I'm told, and it makes sense in my head. Link to comment Share on other sites More sharing options...
cruiser54 Posted January 25, 2013 Share Posted January 25, 2013 Setting Your 4.0 at #1 TDC With #1 spark plug removed, turn the engine over clockwise using the 3/4" front crankshaft bolt. You will see the degree marks on your front cover. You will see the timing mark on the balancer. Mark them with chalk or white-out. While turning the engine over, put your finger/thumb over #1 spark plug hole. As the mark on the balancer approaches the marks on the front cover, if you are coming up on #1 TDC, pressure in the cylinder will push on your finger. If there's no pressure, you're at #6 TDC and need to crank the engine over until you see the marks coming together and you get pressure. Set the mark on the balancer to the 0 mark on the front cover. Link to comment Share on other sites More sharing options...
Alexia Posted January 25, 2013 Share Posted January 25, 2013 Just mark it when you take it out. The distributor body can only be installed one way and technically provides no adjustment. The rotor turns clockwise about the distance between two poles when pulling it out. I installed my distributor 180* off when trying to start the stroker for the first time. Whirr whirr whirr whirr KABOOM Link to comment Share on other sites More sharing options...
HOrnbrod Posted January 26, 2013 Author Share Posted January 26, 2013 Just mark it when you take it out. The distributor body can only be installed one way and technically provides no adjustment. The rotor turns clockwise about the distance between two poles when pulling it out. I installed my distributor 180* off when trying to start the stroker for the first time. Whirr whirr whirr whirr KABOOM Starting an engine for the first time to me is one of the most important times to set the engine @ TDC compression stroke before installing the dizzy. Just curious Alexia, why didn't you? Link to comment Share on other sites More sharing options...
Alexia Posted January 26, 2013 Share Posted January 26, 2013 Starting an engine for the first time to me is one of the most important times to set the engine @ TDC compression stroke before installing the dizzy. Just curious Alexia, why didn't you? Soooo... I had to take the distributor out to prime the oil pump. I thought I put it back in correctly per my markings, but I got the gear one notch off which messed up the timing enough. I rotated the engine to what I thought was TDC, realigned the distributor, and that ended up putting it in 180* off. Link to comment Share on other sites More sharing options...
HOrnbrod Posted January 26, 2013 Author Share Posted January 26, 2013 K, I can see that happening. I hope you didn't berate yourself too badly. Were it me, I would have been highly POed at myself. :yes: Link to comment Share on other sites More sharing options...
cruiser54 Posted January 26, 2013 Share Posted January 26, 2013 Did this photo link work? <a href=" target="_blank"><img src=" border="0" alt="Photobucket"></a> Link to comment Share on other sites More sharing options...
gogmorgo Posted January 26, 2013 Share Posted January 26, 2013 No. Copy that second link you've got (the img src one) and paste it into the box that shows up when you click . Should work. Like this: Image Not Found To make it a link, select the picture once you've got it into the text box here, and use the button two to the left of the image button. It looks like three links of chain with a little plus. Link to comment Share on other sites More sharing options...
HOrnbrod Posted January 26, 2013 Author Share Posted January 26, 2013 What has this to do with the topic? Link to comment Share on other sites More sharing options...
gogmorgo Posted January 26, 2013 Share Posted January 26, 2013 Wondering that myself. Guessing you can see the timing marks on the harmonic balancer? Link to comment Share on other sites More sharing options...
cruiser54 Posted January 26, 2013 Share Posted January 26, 2013 What has this to do with the topic? Just the timing marks and me experimenting with posting photos. Link to comment Share on other sites More sharing options...
Biotex Posted January 26, 2013 Share Posted January 26, 2013 Not sure if the comanche 4.0l is the same as on my 06 TJ 4.0l but you can not see the timing mark without loosening the belt. Not sure what the engineers were smoking that day, but I just remembered this tidbit. I replaced the OPDA (oil pump distribution assembly) aka the distributor, and being old school, I proceeded to find TDC like I have done thousands of times before on other engines. With the computer controlling the spark, boy have things changed. The more I think about it, the more I feel that just marking the rotor and housing is the only way to go "IF" you aren't going to rotate the crank any. Link to comment Share on other sites More sharing options...
HOrnbrod Posted January 26, 2013 Author Share Posted January 26, 2013 Just the timing marks and me experimenting with posting photos. Okay, I just was curious. Cruiser, Is this a 4.2 oil pan? It looks deeper and is has reinforcing flutes on the sides. Mine is just smooth w/o flutes. Image Not Found Link to comment Share on other sites More sharing options...
cruiser54 Posted January 26, 2013 Share Posted January 26, 2013 Okay, I just was curious. Cruiser, Is this a 4.2 oil pan? It looks deeper and is has reinforcing flutes on the sides. Mine is just smooth w/o flutes. Image Not Found 4.0 oil pan. Link to comment Share on other sites More sharing options...
Alexia Posted January 26, 2013 Share Posted January 26, 2013 Not sure if the comanche 4.0l is the same as on my 06 TJ 4.0l but you can not see the timing mark without loosening the belt. Not sure what the engineers were smoking that day, but I just remembered this tidbit. I replaced the OPDA (oil pump distribution assembly) aka the distributor, and being old school, I proceeded to find TDC like I have done thousands of times before on other engines. With the computer controlling the spark, boy have things changed. The more I think about it, the more I feel that just marking the rotor and housing is the only way to go "IF" you aren't going to rotate the crank any. That would just be a difference in harmonic balancers. I can find the timing marks on my 2004 LJ fairly easily without loosening the belt. Okay, I just was curious. Cruiser, Is this a 4.2 oil pan? It looks deeper and is has reinforcing flutes on the sides. Mine is just smooth w/o flutes. Image Not Found Looks just like my aftermarket Dorman oil pan. Link to comment Share on other sites More sharing options...
HOrnbrod Posted February 1, 2013 Author Share Posted February 1, 2013 Installed the NOS 94-99 dizzy today since I'm getting a code 54 (Distributor sync pickup - Change sync sensor in distributor). Picked up a new Mopar unit for just a little more than buying a new sync pickup for the original unit. Anyhow, got her in and clocked right, plugged all the wires back in, and crank/crank/crank with no start. Rechecked everything about umpteen times, even reset the dizzy using the TDC compression stroke procedure. Was getting pissed and suspected the new dizzy pickup was bad or it had a compatibility issue with the 91 system and was going to throw the old distributor back in just to see if it would start. But tried it one more time after rechecking again and mistakenly put the old dizzy cap on. BOOM, started right up instantly. The The 91-93 and 94-99 distributors are completely different. They use the same cap but the rotor is different. I noticed I had put the old cap on, the engine ran fine, and immediately deduced something might be wrong with the new cap. Clever, right? :idea: Turned out that the carbon push button in the cap that the rotor rides on was completely disintegrated and stuck and I had an good sized air gap on the dizzy output to the coil. :doh: I guess after twenty years or so sitting on a shelf stuff happens. Three hours to complete what is normally 30 minute job. Lesson learned. She runs great now w. no more fault codes. Link to comment Share on other sites More sharing options...
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