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Jeep 4.0 timing gear location problem setup
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bioguy
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Mar 6, 2010, 2:24 PM
Post #1 of 21
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Jeep 4.0 timing gear location problem setup
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Have 95 jeep grand cherokee with 4.0 straight 6 engine. new timing gears & chain. when I align markes together with engine at TDC, it only lines up with # one cylinder on TDC exhaust stroke? When turning crank it goes to # one TDC compression 180 Degrs from marked together? Wondering if other mechanic had removed the cam gear dowel pin and installed in wrong hole? Ussualy it is assumed that the TDC is compression stroke? No matter how I turn the cam to match with the gear together marked it rotates to fire at 180 degrees off? Any words on this issue?
Problem is 50 hrs of work by other mechanic and do not know what they did other than worked on the timing chain. Engine runs but needs throttling to keep but backfires through TBY and heavy hits of exhaust. Wondering if they had removed the dowel pin and installed in wrong hole? OR does it make any diff what TDC # one cylinder is in.
Engine appears to be firing with intake and exhaust valves not closed. They did have the distributor about 5 degrees off and not locked with bolt to fork. I made that correction but it ran even worse.
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Hammer Time
Ultimate Carjunky
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Mar 7, 2010, 3:43 PM
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Re: Jeep 4.0 timing gear location problem setup
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Now, how is that possible?
If the piston is at top dead center, it will take a complete revolution to be at TDC again. It certainly won't be at TDC if you only turn it 180 degrees.
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bioguy
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Mar 8, 2010, 2:16 PM
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Re: Jeep 4.0 timing gear location problem setup
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tHANKS BUT THE MARK i AM TALKING ABOUT IS THE MARK ON THE CAM SPROCKET AT 180 DEGREES. If I line up the crank sprocket to #1 TDC stroke and then install the cam sprocket with chain to point at the crank mark I have now made the TDC the exhaust stroke? The TDC commpression does not come for fire till the cam mark is now 180 degrees from the crank gear? I am wondering if the mechanic that worked on this thing ( he did not fix) had taken the cam shaft dowel pin out and re-installed in wrong hole? That is the only way you could get the cam shaft to fire on the TDC compression stroke and have marks pointing at each other...orrrr does it matter??? I am in the dark as to what may have been done to this timing deal. It does have #1 spark plug rotor to #1 fire when the mark is 180 degrees away. Wondering if this is or would be an issue when buttoning it up to see if I have cured the problem stated??
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bioguy
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Mar 8, 2010, 4:13 PM
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Re: Jeep 4.0 timing gear location problem setup
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Sorry for confusion. The cam as it is now with the dowel pin in its current hole will only allow the cam to go to TDC compression when the Cam gear mark is at 180 degrs away from the together marked with crank gear. Cam shaft does have two holes with a roll pin in one and the other hole is 180 degrees from it. I do not know if they had removed the pin or not. As it stands, the cam will always go to the #1 compression TDC at the 180 degree mark of together with CRANK GEAR MARK?? Event= crank gear to TDC ( whatever it is exhaust or compression) Marked dot of crank gear is pointing at the cam gear mark when put in place ( dowel pin allows only one install possition) Now, when I turn the crank gear it starts the rockers of #1 cylinder to start the intake valve open run and does not stop till the cam gear mark has now moved to 180 degrees of its origional start and the #1 cylinder is now in TDC compression? Only way to make the marks line up together at TDC compression would be to have the dowel pin in the other hole that is 180 degrees on the cam shaft.
Does the timing require, that when the cam gear and the crank gear marks are together that is should be the TDC compression stroke it is in at that time? So when you crank the crank gear it would be at the exhaust TDC stroke 180 degrees out ( crank gear is two to one of cam)? I do not know if it matters. TDC is normally figured to be at compression or at least most times. The manual does not specify but only states TDC #1 cylinder?
Sure wish I knew what the other mechanic did before he gave up on this thing as it is for my sister-in-laws. I am hoping that the timing chain and redoing the gears will solve my problem. I have checked all sensor, cam, crank, TBS, coolant, for both voltage and signal voltage with no failures. This thing does not throw a code either. If I have same screwed up running after timing install I will look at poss PCM. Just wanted to know if TDC is interchangable with cam or if poss dowel change. I am watching this posting as hope to button up tonight. I will check back before.
Thanks again for any thoughts you may have on this issue. I have two racing mechanics dealing with it also but the thought seems to have never come up?? I do not think of any sensor that would know the diff of the TDC's in the timing area as long as #1 cylinder was at firing with distributor.
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Hammer Time
Ultimate Carjunky
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Mar 8, 2010, 4:26 PM
Post #6 of 21
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Re: Jeep 4.0 timing gear location problem setup
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The whole thing is just making no sense at all. Alldata has no mention of other possible positions for the cam gear and I would be very shocked if it was even possible.
There is no question as to the position of the crank. If the piston is at TDC, the either both valves have to be closed (comp stroke) or the exhaust valve is open (exhaust stroke). Those are the only acceptable options. If it's anything but that, then you have some wrong parts in there.
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bioguy
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Mar 8, 2010, 5:24 PM
Post #7 of 21
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Re: Jeep 4.0 timing gear location problem setup
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What I am saying is this= No matter what you do with the gears, both cam or crank, the possision of both marks pointing together is only poss ( as the system is now) when the TDC is in the exhaust stroke. Meaning the first movement from that poss when cranking the engine is intake valve opening. Only way to make it be the TDC compression when marks are together would be to switch the dowel pin to the opposing hole on the cam. This may have been done by mistake as it is now???
Question is, when the marks on both gears are lined up pointing at each other, is the TDC supposed to be compression TDC ???
I am now going to check to see if a new or mis placed dowel pin is making the cam 180 degrees off. Hope this is better to understand.
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Hammer Time
Ultimate Carjunky
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Mar 8, 2010, 5:41 PM
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Re: Jeep 4.0 timing gear location problem setup
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If you are at TDC with the exhaust valve open, then you are in time. You will just have to move the distributor to match. They could have moved the dowel but it doesn't matter. Rotate the crank one turn and your at TDC compression where you have to set the distributor. It will work either way and the marks aren't important.
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bioguy
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Mar 8, 2010, 7:09 PM
Post #9 of 21
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Re: Jeep 4.0 timing gear location problem setup
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I think that is the case with this engine. Seems as others in some other forums have the same thing and maybe the way Chrysler does it. We will set the marks together with TDC in the exhaust stroke and then button up. Do the TDC in compression stroke and set #1 in distributor. Origional guys may have replaced this timing set ( the chain, gears are new) and installed with still mis-positioned cam ( maybe a couple teeth skipped) without doing a good job of timing it and thus giving a slight off lob possition giving the caugh up carb and out exhaust. Sounds reasonable and I hope it is it. If not I will look at the cam sensor as testing it for signal voltage at cranking only says it signals..but is it signaling at the right time from the PCM, thus pre-spark with valves still a bit open?? I will let you know what I find on this thing. I have had to smoke a few cigars while thinking on this one.
Thanks for your help.
Regarding other post:
A bit confused on the three wire oil sender not having anything to do with the pump relay. I have read in a few posts and some sensor manuals that this type of oil sender was a protection to not burn up an engine if oil pressure was lost. I do not know if they are saying all three wired senders but maybe some? It is always good to get as much info on things as poss.
Thanks again.
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Hammer Time
Ultimate Carjunky
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Mar 8, 2010, 7:29 PM
Post #10 of 21
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Re: Jeep 4.0 timing gear location problem setup
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That is a common misconception that just because the oil pressure switch is in the circuit, it must be there to shut the engine down but it is not. You can totally remove either the fuel pump relay or the oil pressure plug and it will stay running. Without the relay, it will just have a long crank until it builds pressure. That vehicle isn't even wired that way to the oil pressure switch anyway.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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re-tired
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Mar 8, 2010, 11:54 PM
Post #11 of 21
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Re: Jeep 4.0 timing gear location problem setup
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Here is a way of setting up the cam . Note the postion of crank keyway and mark on cam sprocket. To install:
- Assemble the timing chain, crankshaft sprocket and camshaft sprocket with the timing marks aligned.
- Install the assembly to the crankshaft and the camshaft. Install the camshaft sprocket retaining bolt and washer and tighten to 80 ft. lbs. (108 Nm).
- Check the alignment of the chain and sprockets by counting the number of links or pins with the sprockets positioned as illustrated. There must be 15 pins between the marks on the sprockets.
  
Fig. Fig. 8:
4. After Verifing by counting chain links as shown . Then turn eng over , feeling for air at #1 plug hole . Install dist. , rotor at #1 wire.
LIFE'S SHORT GO FISH
(This post was edited by re-tired on Mar 9, 2010, 12:29 AM)
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bioguy
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Mar 10, 2010, 5:12 PM
Post #12 of 21
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Re: Jeep 4.0 timing gear location problem setup
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Well, did some checking on this issue and found an interesting deal. All three of the manuals and all looks at web forums on the cam gear and crank gear timing marks. I think the timing kit may be even the wrong one that the original guys put in. I find that I have 20 pins when I do the 1 and 3 position sooo, I am going to take this one in and see if it matches another for the jeep. I do not know if they make a chain set that may be smaller or what but the 15 pins is pretty much the thought by most.
Sure is fun working on something someone else has messed with. I was assuming the other mechanic knew his stuff but I did find at first the distributor was off and not in the fork to clamp position soooo I decided to look at it from scratch. I will let the forum know what I find.
thanks guys.
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bioguy
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Mar 11, 2010, 9:03 AM
Post #13 of 21
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Re: Jeep 4.0 timing gear location problem setup
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Re-tired= thanks for the dia. I have them already but you stated in the last, like I have always thought, the timing marks are together at #1 TDC compression and the way this is set up is TDC Exhaust. Now, as stated just last, I have a chain/sprocket set new that was installed by another. The links are not roller chain but heavy duty type with tighter teeth .NOW...The only way that I can have TDC On compression is if the cam dowel pin has been located into the wrong hole ( two holes accross for each other) OR>>> I have the wrong gear setup with the cam gear dowel hole on the opossite side?? Going to be looking this over before any button up. I have read about the issue on another forums with the Chrysler being, it seems, TDC marked at exhaust but not sure yet. The condition of the engine when it did run was only footing the throttle to keep running and exhaust blasting out pipe and up through intake.
This is why we thought the timing gears were off to start withas when we put the marks together we had exhuast not commpression thus the thinking they had installed the chain 180 degrees off. Just letting you know more if it helps as I know its fun to keep the thoughts going.
Let you knw moire later
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bioguy
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Mar 11, 2010, 2:37 PM
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Re: Jeep 4.0 timing gear location problem setup
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Ok, I just did the matchup at an auto zone and the current timing set is the same as a new replacement ( that is what it is) the count 15 pins will never work on this chain as they are heavy duty none roller chains and the gears are a gear tooth type. It does not mean yet that the dowel pin was removed or loose at the time and installed into wrong hole nor if it makes any diff. We will install Sat and try a run, hoping that the gear was installed a couple teeth off. If she runs the same we will get back in to sensor and PCM checks for a problem.
This engine has 129K on it and has new plugs, wires, cap,rotor and of course time set.
Will let you know more after sat.
Thanks again guys.
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bioguy
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Mar 12, 2010, 9:25 AM
Post #16 of 21
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Re: Jeep 4.0 timing gear location problem setup
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Thanks for the pics and that is what I will deal with when I get to that portian. I am starting from scratch as I do not know what the other mechanic has done other than he did put in a new timig gear/chain set ( checked for correct set and it is).
I first have to make darn sure that he did not touch the dowel pin on the cam shaft as that would be the only way I could have the condition of timing marks lining together at TDC exhaust stroke.
The problem with not getting this delt with is that if I was to be 180 degrs off and the crank sensor has three equaly spaced indicator marks on the flywheel I could be having the problem of PCM not being able to get a real TDC compression possision.
I understand the damper deal and that will be looked at after I have buttoned up the time gear issue.
Sure is frustrating that with all the web forum searching done I have not found one thread that says the TDC with #1 when the marks line up should be at compression stroke.
Every one seems to side step that with just saying the TDC #1 cylinder?
I am thinking it may be right, in the exhaust mode as many are asking the same thing in my searchs but again no real answers.
Simple way to put it is= does the crank shaft possision sensor have to have the TDC at marked gear together in compression stroke to make sure the PCM is not confused for firing #1 cylinder? I can understand the idea of cam shaft being marked to match the TDC but will the wrong TDC be a problem in crank sensor reading?
Nice fish.
I can not wait till the gills are on their beds this spring here in MI.
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re-tired
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Mar 12, 2010, 3:09 PM
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Re: Jeep 4.0 timing gear location problem setup
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Now your starting to confuse me.
1) crankshaft - crankshaft has a reference mark on its gear which is ALWAYS at it proper postion when the #1 piston is at the top of its stroke .
2) The flywheel can only be bolted on at one position. The slots on the flywheel for the crank position sensor will ALWAYS tell the ECM that the crank is at the top of its stroke, it does not care where the cam or valves are.
3)The cam shaft is ALWAYS installed at a position where BOTH valves are closed and the crank is at the above setting
4) the timing chain is installed while condions 1,2,3 are met
5) the dist is installed with the rotor pointing at the plug wire for the #1 cyl
6) "All" of the conditons 1,2,3,5 will only happen again on the next firing stroke of the #1 piston the other times that the #1 piston comes up one of the events will be missing .
This is how it happens and will always happen.
LIFE'S SHORT GO FISH
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bioguy
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Mar 12, 2010, 5:35 PM
Post #18 of 21
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Re: Jeep 4.0 timing gear location problem setup
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I understand the crank position sensor's function but I wanted to know if it would give false info to PCM if the cam was not set at timing marks together on COMPRESSION TDC #1 cylinder.
I did talk now to the mechanic and he told me what he had did and he did not move the cam dowel pin sooo. now I know that all the forum hunting I did on this issue and all the people that had the same TDC questions as they had found themselves is not wrong. Apparently Chrysler does it this way I guess. So i will button up Sat and see how things progress. Your thought on the damper is a good one and could very easely drive out the timing enough to give valve open condition during fire. Will look at that very carefully if the re-alignment of time set does not repair.
I have tried to give as much info as poss. but the TDC happens 2 out of the four cycles with TDC at exhaust once and again at compressionTDC. Timing marks together on this engine puts TDC in exhaust stroke not compression stroke for firing.
I now know we have new crank sensor, timing gear/chain set, rotor, cap, plugs & wires. The PCM has been switched to see if it was the problem but was not.
I will now button up, TDC compression for #1 cylinder, set rotor/dist right and see if it works. If not, I will check for actual TDC #1 compression with guage and check the damper mark. If that fails I will check distributor very carefully for faults along with cam sensor. If that does not repair then I will be doing a very carfefull wiring check to make sure I am not having a sparatic short or looseness problem.
Having fun though.
Thanks for your help and I will let you know what it is when I find it.
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re-tired
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Mar 12, 2010, 8:09 PM
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Re: Jeep 4.0 timing gear location problem setup
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I have tried to give as much info as poss. but the TDC happens 2 out of the four cycles with TDC at exhaust once and again at compressionTDC. ****************************************************************************************************Remember the piston will come up to the top of its stroke mutiple times but only ONE time will all events 1,2,3,5 happen at same time . This is TDC of the compression stroke, the plug will fire , the piston will go down - POWER stroke , travel back up - EXHAUST stroke , back down - INTAKE stroke , back up - COMPRESSION stroke , now your at TDC AGAIN ! FOUR CYCLES - TWO TDC's........ONE TDC COMPRESSION STROKE LIFE'S SHORT GO FISH
(This post was edited by re-tired on Mar 13, 2010, 11:48 PM)
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bioguy
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Mar 13, 2010, 8:47 AM
Post #20 of 21
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Re: Jeep 4.0 timing gear location problem setup
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Well we are in my shop and starting after I type this post. We will procede as stated in my last post and let you know how things go. Have a good fishing trip.
Thanks
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Hammer Time
Ultimate Carjunky
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Mar 13, 2010, 1:21 PM
Post #21 of 21
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Re: Jeep 4.0 timing gear location problem setup
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You seem to just insist on complicating something that is simple. As I told you about 3 pages ago, it doesn't matter if the dowel has been moved on the cam if they are 180 from each other. It will be in time in either position. The only thing that will effect is the distributor position so that may have to be moved
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