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Discussion Starter · #1 ·
Replacing the timing chain and sprockets on my 97' 2.5 TJ. Somehow things got turned and now I can't get the sprockets to line up! What is the order of operation to make sure my timing is correct from this point? I can turn the crank shaft and I can turn the cam but I have no idea how to corilate the two correctly. The book has me doing things without there being anyway to get things exactly right. It says that you can double check the chain placement by putting the "camshaft sprocket timing mark at one o'clock, count the chain pins between the two timing marks - there must be 20 pins." How do I know exactly where one o'clock is?! You start with everything at top dead center and the rotate everything to line up the timing marks on the sprockets. How do I work backwards from there to get this thing back together??
 

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Discussion Starter · #2 ·
When the timing marks are aligned on both sprockets should the engine be on top dead center on the exhaust stroke? (Distributer is pointing at number 4 and front piston is at tdc). What is the proper way to rotate the camshaft sprocket timing mark to one o'clock? Is this looking straight at the engine with the sprockets and chain in place? I want to get this right. Can someone who knows, please give me clue...
 

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I just put the crank at tdc and put the cam so the distributer is pointing at number one point. Put the sprockets and chain on. I then spun the crank to bring the timing points together. (This brings the engine to tdc on the exhaust stroke with the distributer pointing and number four point. I think this is what threw me off) I then rotated crank to align cam timing mark at one o'clock and twenty pin count was good. That's the best I can do. Someone stop me if this is in correct.
 

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Timing Mark Alignments

I thought I might find my answers in this thread, but doesn't look active for a few years. I have a 1995 2.5L XJ and I had the lower block machined and assembled. I went to confirm the timing and this is where I need some help. The crank and cam sprocket marks are aligned together but not when the #1 is at TDC. When #1 is at TDC, the Crank Sprocket timing mark is pointed to the centerline of the CAM, but the Cam sprocket is pointed in the opposite direction. Should these marks be together at TDC or does that matter? One other detail... when setting the CAM mark to 3:00 there are 20 pins between the Cam mark and the Crank mark, just like the manual says there should be. just confused.... I thought the Timing marks on both sprockets needed to be together at TDC. Were the timing sprockets not installed right?

yep, I made sure as I was at TDC on the pressure stroke. When I roll the crank around another turn, the timing marks come back together, but it isn't at TDC. Does that sounds right?
 

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The piston hits tdc twice for every rotation of the cam shaft....
Thus as the engine rotates the dots will alternate together (at tdc) apart (at tdc) together apart etc

Position of the crank alone determines tdc.... position of cam determines compression or exhaust stroke
 

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You are at TDC piston one on exhaust stroke rotate crank one full turn so cam rotated one half turn and cylinder one will be at TDC compression and marks will align

You have a four stroke engine so cylinder one is only on TDC compression once for ever two full rotations of the crankshaft


Sent from my iPod touch using Tapatalk
 

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The procedure to set timing on these engines is the most asinine bassackwards procedures I've ever encountered. It runs complete opposite of almost any engine as far a logic is concerned.

That being said... align your marks like you would any other engine but do NOT pay any attention to the Camshaft Position Sensor location unless you've removed it from the engine. Once you have the marks lined up and bolts holding the cam sprocket in place turn the crankshaft until your marks look like they do in that picture. Like i said, it looks 180 degrees off, but it is correct. I fought with putting my logic aside last year when I did this project.
 

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Being that the lower block was machined, don't you reckon the distributor was removed in the process?
That was NOT the original poster's post, it was a post he found similar to his issue. He did not state HIS lower block was machined.

Regardless, the CPS points to the #4 cylinder when the timing marks are aligned as stated in the Factory Service Manual. It is a stupid design. So, unless he took the "distributor" out of his engine he doesn't need to worry about that.
 

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Hello... thanks for all the info. It is helping me out a lot. Tossing logic out the window would indeed make this job a lot easier!:bop: So, for the record, I did get the block machined and the distributor was removed, but I think getting that back in on time won't be too much of an issue.

"the CPS points to the #4 cylinder when the timing marks are aligned as stated in the Factory Service Manual"

Didn't see that in my Service manual, but Makes sense now in a very awkward way... I will make sure the rotor is on the #4 when these marks are aligned.

Just to be sure I have got this right, and hopefully to help the next logically challenged, I am going to post some photos showing the Crank/Cam and Valve position relation through the cycle.

Step 1.pdf
Step 2.pdf
Step 3.pdf
Step 4.pdf
Step 5.pdf

Let me know if these look good to you. If so, can be referenced by the next logically challenged.
 

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"the CPS points to the #4 cylinder when the timing marks are aligned as stated in the Factory Service Manual"

Didn't see that in my Service manual...
That would be because you are getting advice applicable to an engine that you do not have. It's an internet thing.
 

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Just to be sure I have got this right, and hopefully to help the next logically challenged, I am going to post some photos showing the Crank/Cam and Valve position relation through the cycle.

Step 1.pdf
Step 2.pdf
Step 3.pdf
Step 4.pdf
Step 5.pdf

Let me know if these look good to you. If so, can be referenced by the next logically challenged.
TDC #1 cylinder compression is at step 3. On steps 1 & 5 you are on the overlap between the exhaust & intake cycles which is also at TDC but #4 compression. On the overlap cycle both valves are actually open slightly. Either way the marks align at TDC #4 compression. It is not the only engine to do it that way. You are good as long as you set the distributor pointing to #4.
 

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I'm going to try to revive this old Post because I'm confused LOL does this apply to a 99 2.5? And do I understand it correctly that the timing chain is installed with number 1 at TDC on compression with the dots lined up and then you put the distributor in with number 4 on TDC on compression and rotor pointing at 4?
 

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I doubt they changed it between ’95 & ’99 but you can remove the cover & see where the marks are as you turn it to get compressing on #1 as you get it to TDC.

I think you will find at #1 compression when you are at TDC the cam mark will be opposite the crank mark as seen in step 3 above. Then when you get to TDC with the marks lined up compression will be on #4 as seen in steps 1 & 5 above. If so you need to install the sprocket with the marks lining up to be sure it is timed correctly then turn the crank one turn (cam mark away from the crank mark) getting it to #1 compression to set the distributor pointing to #1 using the FSM procedure to position it.

Note the explanation in post 15 above. Also why I added this to what I posted to your other thread. On post #15 add, “or rotate the crank 1 full rotation then point the distributor to #1.”


This question comes up from time to time so post results from your ’99 to help other with this same question.
 

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Just a quick question guys I have a 1990 2.5 yj with the tbi.I have the timing marks set as explained above with the cam sprocket mark as in pic#3, I want to now install my distributor. For the tbi yj it says to put on the crank pulley after tdc is set and then allign the mark on pulley to 0 mark on timing cover, then drop in distributor so the rotor is facing 6 o'clock is this correct? Or should I just put the distributor in facing #1 spark plug when everything is like in pic 3 above. Asking cause I know the tbi procedure is different. Any help is appreciated, thanks.
 

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The procedure to set timing on these engines is the most asinine bassackwards procedures I've ever encountered. It runs complete opposite of almost any engine as far a logic is concerned.

That being said... align your marks like you would any other engine but do NOT pay any attention to the Camshaft Position Sensor location unless you've removed it from the engine. Once you have the marks lined up and bolts holding the cam sprocket in place turn the crankshaft until your marks look like they do in that picture. Like i said, it looks 180 degrees off, but it is correct. I fought with putting my logic aside last year when I did this project.
Im having this same issue. Got timing chain all lined up! but its on exhaust stroke. And at #4 so im lost! What do i gotta do 2 get it 2 run right? Or at all lol.
 
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