I checked the Engine Compression on my 97 XK8. Throttle wide open and Engine warm. Came up with 95psi give or take a couple psi on all Cylinders. Can't find what is it supposed to be. Is 95psi good or not? Cheers!

 

What prompted you to do a Compression Test?

If you suspect a Cylinder Head Gasket failure, then even readings (plus or minus 2 psi) is good news.

If you're concerned about blow by, then a Leak Test is what you want.

Check this link for info:

How to do Cylinder Leak Down Testing- Car Craft Magazine

A figure of 120 psi sticks in my mind for compressions but I can't find a source reference for this.

Graham

 

95 psi seems pretty low. That reading could be caused by not enough cranking time, an improperly calibrated compression guage, low cranking speed, and engine problems. I would be hesitant to blame the engine.

I found info that a 97 AJ26 should show around 160 after reaching maximum compression reading. This should be obtained after approximately eight seconds of cranking, according to the info I read.

My technique is to crank it with a battery charger attached to maintain good cranking voltatge during the test. I crank it to see 5 compression cycles on the guage for each cylinder. I note the 5th compression cycle psi. The first compression cycle will be read much lower than the 5th.

More important than the max psi is the variation between cylinders. 10% variation is the max to look for before you suspect a problem.

If you have low readings or variation exceeding 10%, GGG's idea of a leak down test is a great way to find out where your compression is being lost.

Like GGG, I'm curious as to why you're checking compression.

 

I have a 97 XK8 with the the Nickasil Cylinders. I was checking to see on the wear of the Cylinders, I thought that is what you do. The reason to check is my Oil consumption, it was at 1qt per 1k miles. Seems a little high. Replaced Valve cover seals and checked all Airbreathers. Got it down to 1/2qt per 1k miles. While doing all that why not check Spark plugs and check Compression. I might not cranked the engine long enough. Will try the Blow-by test. Thanks for all the input.

 

You're doing the right thing. I was taught many years ago that the compression test was essential to determine the basic condition of the engine. The leak down test is good to determine where your compression loss is going. This still may not tell you about the oil burning issue. Maybe it will tell you if you have to get rid of this Jag and get another.

I had a 98 VDP. Oil consumption issues like yours. Nikasil engine. I found a guy that was more than happy to drive my gorgeous, comfy VDP and put a quart of oil in once in a while. He was not a high mileage driver like me. I found a 2001 XJ8 and got it running. I'm very happy now.

Keep doing your evaluation and make an educated decision on your next step. We're here for you, man.

 

Opinion from this end of the scale; nothing wrong with 2000 miles per quart of oil. How many miles on your car?
Is it running smooth?
Any burning oil smell or drops on the ground?
I'm getting about 1500 per quart these days; running smooth with a slight and occasional oil burning scent like leaking valve covers dripping on the exhaust manifold. I'll get around to valve cover gaskets this winter.
Next check give it at least five compression strokes before noting the reading.
And, before the check, run the engine for 30 seconds to wet the cylinders as opposed to doing it after setting overnight. Do one side then run it again before doing the other side. On a nicely aged engine it will make a difference.
Mike
..might check my compression some time this winter just for fun.