How do you check the timing on a 2000 XJ8 (AJ 27 engine)? I expect you install the crank plug and check to see if the flats on the intake and exhaust cams are level. Since degrees matter here, is placing a straight edge on the flats accurate enough to determine if they are level? If the engine is determined to be out of time how many degrees is too much and what is the procedure for correcting this condition. Thanks!

 

Have a look at the pictures in my brand new thread regarding timing chain swap:
https://www.jaguarforums.com/forum/x...e-swap-266724/

You'll also find pix there of the flats, and will notice that they were NOT THAT FLAT anymore after 25 years, and nevertheless there were no troubles with the engine.

If you can manage to put that crank plug in, then yes: Sure. Tell me how you do that, when the engine is still in the Jag and the access to that sensor is blocked with a pipe and wires.

If just want to have a look at the flats with the cam covers removed, just turn the crankshaft clockwise until you are there - you do not need a plug for that.

 

Peter,
Thanks! Installing the crankshaft plug on my 4.0L was relatively easy, plenty of access. I read your excellent write up(s) but didn't see any photos??? I changed my secondary tensioners via the remove exhaust sprocket method (I used cam locks and the crankshaft plug) and, upon completion, one bank of flats appeared to be nearly perfectly level, at least as far as I could tell by eye and by laying a straight edge across them. The other bank, may have been slightly off or it could just be my imagination. Now it seems the valves may be just slightly more noisy and the idle is very slightly rougher. So do you think the flats being very slightly off on one bank is a problem? Is it worth loosening the exhaust sprocket on the suspected bank and retensioning/retourquing it with the locks and plug installed? Would that even help? Thanks again!

Jim

 

A couple degrees is not going to cause a rough idle, but you may have a air leak . Check the fuel trims. Increased valve noise is possibly just because you're listening more carefully.

 

Peter,

Thanks for he sage advice! No other Jag people around here to exchange notes with. LTFT and STFT around +5%. I bumbed a smoke machine off a friend and will look for a vacuum leak this week. Agreed some of this may just be in my head! Ill keep you posted my friend (mate in Australian)!

Jim

 

LTFT 5% is good, no significant air leak. I wouldn't go looking for trouble.

 

When you tighten the exhaust cam sprocket bolt, you load the cam to the 'timed' position.
When the holding tool is released, the natural valve spring tension will drive the cam into a slightly 'reversed' state at rest.(chain slack on one of the heads)

The OIL PRESSURE and rotational force will keep the cam 'timed' under engine operating conditions.

A running engine will NEVER run in the opposite direction until the engine is shut down and comes to rest.(compression causes the crank to 'rock' slightly)

45 degrees AFTER TDC is timed and forget all else.

 

The days of timing lights and rotating the Distributor Cap
are coming to an end but I still have a few cars i need to
do that with.