Pretty new to the whole Jag experience, but here's the situation...
A 2000 XJ8L literally fell in my lap -- I have essentially towing expenses invested in it. 101k miles, and it doesn't run, but turns over. Ran compression tests, came up with the following:
#5, 80 psi. #6, 80 psi. #7, 50 psi. #8, 80 psi. I would attribute this to being parked for 5-1/2 years, rings stuck. However.........
#1, 0 psi. #2, 120 psi. #3, 120 psi. #4, 0 psi
So obviously we have a problem.... I have downloaded the excellent step-by-step timing chain job from Black Onyx (THANKS!!), but I also read something about removing exhaust cams and running compression to determine if any valves are damaged BEFORE pulling a head. I also have a factory manual, and just received the cam and crank tools required to do the job. Everything else I could possibly need is already in my tool chests... I'm preparing to tear into it this weekend to determine the next steps in reviving the engine.
My question is, by the time I get deep enough to remove an exhaust cam it seems ill-advised to try and crank the engine over. I'm assuming the writer meant BY HAND, and not with the starter? Following that line of logic, how much hand-cranking will be necessary to identify any meaningful compression numbers? I've torn into engines before, but never tried to run compression on one that's partially disassembled...... Usually I've just figured the head(s) needed rebuilding anyway and took it (them) off. Which I am fully prepared to do, but if it can be avoided I'm OK with that too.

Thanks
-Steve-

 

I really think it is ill advised to crank the engine. Before disassembly you need to installed the crankshaft locking plug that goes into the flywheel to lock the position.
I think the test you are referring to is called a leaked down test. You remove the cams and then apply air pressure to each cylinder thru the spark plug opening and check it for leaks. If the valve for a cylinder is bad or the seat has dropped you will get air blowing out the exhaust or the intake and the cylinder won't hold pressure. If a valve has contacted the piston and bent it will show right up.

 

Oh, yeah duh.... Different gauge..... Got one of those too. I will fiddle with that before pulling the heads. Thanks for jogging the memory.
I'm not opposed to pulling them on general principles, just to check the bores and de-carbon everything. I scoped all 8, and the only marks I could see on the piston crowns were the ones I made bumping the camera into them. No valve-kiss marks at all, so I'm hopeful that at least the thing is salvageable.
Stay tuned...
-Steve-

 

+1 to Vern's analogy, especially the no crank....those 0's on 1 & 4 are not good by any means and would already anticipate head removal. Any 0 means there is nothing to create even enough minimal back pressure to register on the gauge. Could be (as Vern said) a dropped valve, valve meets piston, broken rings and/or sleeve? Even a blown head gasket will have some back pressure. Have you pulled the valve covers? ...they are the quickest to remove and it'll be need to be done anyways. What about your oil, ...any discoloration? Have you though of pulling the oil pan, its super easy and you'll be able to look up into the cylinders.

 

Highhorse, All I've done so far is pull the plugs and do a compression test. I didn't want to go any further until I had a manual (pdf now in-hand. Or computer...) and the cam and crank tools (arrived yesterday). Agreed, the very next step is to pull the cam covers and take a peek. The oil looks and smells fine, other than being 6 years old... There is no indication of a blown head gasket. Honestly, I think #1 and #4 have damaged valves and I'm headed for a rebuild with new valves and guides. It'll be interesting to find out what's going on in there
-Steve-

 

Well, the oil being good is a plus, pretty much eliminates any penetration to the cooling system. I believe your correct about the valves, I am interested as well in what you find. I like your attitude about this, lots of people come here expecting a magic wand solution.

Here's a thread to look over, just to give you some info. Count Iblis's info is invaluable and he provides some great insight.... https://www.jaguarforums.com/forum/x...ebuild-131732/
Also, have you downloaded the Tech Files from the How To section?...just prompt the link in my sig if not. Here's a site to bookmark also... http://www.jagrepair.com/Default.htm