XJ XJ6 / XJR6 ( X300 ) 1995-1997

Jumped timing chain

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  #1  
Old 01-23-2016, 11:47 AM
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Default Jumped timing chain

Well it can happen, just look how far it has jumped! The marker on the cam "should" be at the very top with the crank is at Top Dead Center.
Obviously it doesn't start and backfires through the inlet manifold.




Scoring on guide is scary.




Just look at how much slack was in it


Updates to fix will follow...
 
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Old 01-23-2016, 12:36 PM
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Scary.

Do you know the circumstances when it failed - start-up?, full throttle?
 
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Old 01-23-2016, 12:53 PM
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Seriously? I'm a bit shocked.

I've only seen this twice with non-performance cars. Once with a Ford I had that, if you can believe it, a heavily coated with nylon camshaft gear.

The other was with a car with, if you can believe it, aluminum camshaft gear.

How did the chain result in so much slack?
 
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Old 01-26-2016, 05:54 PM
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Is it not normal to have a fair amount of slack when the engine isn't running and the upper tensioner is not charged with oil pressure yet?

How many miles on the car?
 
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Old 01-27-2016, 04:21 AM
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Only 131K miles on it, but it would appear the timing tensioner (2nd gen one) is stuck and not moving at all. As per the other thread on here about the 2nd gen one failing, this one has and therefore not keeping the chain under tension.

Luckily there isn't much major damage, a few dints in the piston heads and some slightly deformed valves. All fixable!

It has been rattling quite badly for a while, especially between 1500 and 2000 rpm, so I bought the timing chain replacement kit and was planning on doing it this summer.

It finally went on a cold startup, so not under load which is why the damage is minimal.

 
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Old 01-27-2016, 08:41 PM
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Wow, sorry to hear that. I hope this is a rare and unusual issue. Fortunately I haven't heard of it before in this scenario.
 
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Old 01-28-2016, 04:07 PM
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So the AJ16 is an interference engine. Glad the damage was minimal and repairable.
 
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Old 01-28-2016, 05:28 PM
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Can you provide pix of what went wrong? Stretched chain, broken guide?
 
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Old 01-29-2016, 09:41 AM
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Pleas keep us informed.
 
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Old 01-29-2016, 10:48 AM
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Been at work all week, so will be back on it this weekend - got this far last week, so shouldn't be too much more effort getting the timing cover off, gets dark here to early this time of year!

 
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Old 03-20-2016, 04:22 AM
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Getting there - slowly!

Sump needed to come off so you can remove the oil pump so you can actually get the lower chain off!

 
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Old 07-16-2016, 01:52 AM
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Hello , any update on your car ??????
Thanks a lot and good luck !!
 
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Old 07-17-2016, 12:08 PM
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Getting there (with a few mods and upgrades)

 
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Old 07-18-2016, 04:47 AM
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WahOooo !!!! This is not the same car !!!!!!
Amazing !!
Have you done all the mechanic alone ??
Are you professionnal ?
Have you found a " manual " for this car ?
Not sure yet , but i maybe suffer of a jumped timing belt too ........have a look at this post :
https://www.jaguarforums.com/forum/x...-start-166005/
Any suggestion is much appreciated !!

Thanks , and again congratulations !!!
 
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Old 07-21-2016, 02:31 PM
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Went for a initial start today - not perfect, and needs some tweaking so to speak

 
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Old 08-06-2016, 01:23 PM
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Well all idle problems are now sorted, and it now looks like this, had to remove the 2nd vac pipe from the oil catch tank as I had to relocate the air filter pod (my custom headlights wouldn't fit!) so that will need sorting, but hey it runs smoothly now and sounds beautiful.




 
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Old 08-07-2016, 03:00 AM
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Originally Posted by dfieldsend
Well all idle problems are now sorted
How did you sort the idle issue? And what was causing them?
 
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Old 08-07-2016, 09:28 AM
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A myriad of problems!
Once i'd fixed the vac leaks on the intake side, it was a bit better, but still a bit lumpy, so I then adjusted the fuel pressure regulator to 3 bar from 2.5 again a little better,
Checked and reset the cam sensor by puling out the first spark plug and manually rotated engine to make sure it was TDC, again a little better, by still not right, so finally
changed the crank sensor (again) for a known working one from my donar car and it was almost there. (The crank sensor was brand new BTW)
Then I removed and replaced the "Andy bracket" with a standard bracket and is was perfect - I don't think it liked the extra air flow through the engine with the new ported intake and head.
 
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Old 08-08-2016, 05:55 PM
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Interesting that removing the Andy bracket solved your problem; prompted by the original title of the thread, could you by any chance have fitted the timing chains a tooth or so out of their correct position? It will run quite reasonably, but not quite right. How do I know this? I replaced the top timing chain and set the timing by eye rather than using the camshaft locking tool, and it ran but not correctly.
If you were a tooth advanced, removing the Andy bracket would retard you by about a tooths worth I think. Anyway, alls well that ends well, and congratulations on tracking it down.
 
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Old 08-08-2016, 07:22 PM
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Originally Posted by countyjag
Interesting that removing the Andy bracket solved your problem; prompted by the original title of the thread, could you by any chance have fitted the timing chains a tooth or so out of their correct position?
I also incorrectly timed my engine not too long ago with the Andy bracket still on. It was approximately off by a tooth or so. I contacted Andy and this is what he said (emphasis added):

"If you have my bracket fitted, then you can’t position the missing tooth in line with the sensor to find TDC. However, there are two more accurate ways to find TDC. The easiest, but less accurate, is to use the TDC pointer bolted onto the front cover. There is a white triangle marked on the front face of the trigger wheel in line with the leading edge of the 11th tooth anti-clockwise from the missing tooth. To position the engine at TDC, line up the point of this triangle with the lower edge of the TDC pointer bracket.

The more accurate way it to buy a tool which screws into the spark plug hole on cylinder 1. It uses a dial test indicator to to measure when the piston is at TDC.

Once you have timed the cams at TDC, you can use the camshaft timing service tool to time the cams. Please note that the half engine speed sensor may now be correct or 180 degrees out of position, depending on how far you have turned the engine to find a TDC. You will need to do a search on the internet forums or use the service manual to find information about timing the half engine speed sensor."


"half engine speed sensor" = The round circular object with an observation window on the left side of the engine. To set it properly you just loosen the screw beside it and rotate the whole assembly until the hole is centered inside the circular viewing window.

Though I don't know if after changing the intake manifold significantly affects engine dynamics while installing the said bracket...? something to do with the proper fuel/air ratios and ignition timing...?

I hope that information helps some poor soul in the future

P.S. Thank you Andy
 

Last edited by someguywithajag; 08-08-2016 at 07:25 PM.
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