2002 XJS V8 has be in the garage since Christmas. Went to drive it yesterday and it seemed to turn over freely. Charged the 2 year old battery and it turns over fast but sounds very different than usual. It sounds like it has no compression except maybe on one cylinder. It sounds like all the plugs are out of it when it turns over. It won't fire spit or sputter. Do these things skip cam timming? Are they belt or chain drive to the oh cams? It drove just fine to where it is sitting.
Anyone have an ideas for me?

Jim.

 

Here is a guide to get you started. It sounds like you might have a cylinder wash problem, most common with nikasil lined engines, which you probably do not have, but still a possibility.

https://www.jaguarforums.com/forum/g...d-first-30792/

 

I should have added that fuel pump failures appear to be common after winter storage.

 

Lack of compression = bore wash. Your tensioners will be OK. The engine has a timing chain.
Put a teaspoon of engine oil into at least one bank through the spark plug hole.
Be prepared to run for it if the car's in a garage when it does start.

 

Thanks for the help. I have not had time to work on this thing. I have oiled cylinders before so I get the "run for it" quote. In fact once many years ago someone call the fire department on us doing that.

I will pull the plugs and get out the compression tester asap. I will have a little Marvel mystery oil to go int each cyl as well. *** for the fuel pump, I can hear it running when I first turn on the key. Where is the fuel pressure check fitting? I probably ought to check and see if the rail is pressuring up.

Thanks

Jim

 

I'd try the 'snake oil trick' before getting too worried.
Bore wash will show as very poor compression so testing won't help you much.
The Schrader valve is on the LH fuel rail, about 4" in from the dipstick (blue top).

 

The only thing that bothers me here is why the bore wash unless some other problem kept the engine from firing in the first place?

 

I'm going on what Jim (OP) said
Went to drive it yesterday and it seemed to turn over freely. Charged the 2 year old battery and it turns over fast
which led me to think he'd cranked it on a tired battery then put a new one in.
The only worry would be if the tensioner fairy had visited but
1. It was presumably running OK when put to bed
2. It's spinning over with no horrible crunches
3. If for some bizarre reason the timing has slipped it's too late now anyway.

 

Thanks again

I drove to where it is sitting and ran just fine. I have not looked at it since the battery charge exercise Sunday. No horrible crunching noises. I was not around when my wife first tried to start it Saturday so i don't know about the sound of any damage that might have been done then. Do valves crash into pistons on this engine if the cam timing is off badly?

Jim

 

Yes they do, but it is more likely bore wash. As long as you need to pull the plugs to address a bore wash problem, check the compression before and after adding the oil. But first pull the fuel pump fuse. Compression should be checked with throttle wide open.

 

Honestly just put some oil in one bank.
If it starts it's bore wash, if not there's some diagnosing to do.
If the timing chain tensioners had relaxed enough to let the chain skip one tooth it would start and sound bad, two teeth and your valves have hit the pistons and the damage is already done.

 

I finally got a chance to get to the trouble shooting
Left bank compression 20, 20, 5, 30
Olied the left bank and compression went to 30,30 5, 60 (to me the first three readings are valves not timed properly, but with the back cyl coming up with oil gave me hope)
Put the plugs back in and got a little I want to fire and start but it would not start
I opened up the right bank and compression on the right side was 40 to 60 psi on all four (to me these are bore wash numbers)
I oiled these and she started up in the covered car port where she had been sitting since before Christmas
So it was bore wash
I have oiled cylinders before and the smoke on start is alwasy real thick
Any way all the neighbors came out, someond call the fire department but I was on the phone with them and they did not actuall come.
I drover her for an hour and it is like nothing ever happened. Restarts fine. We wont ever let her sit like that again.
Thanks for the helpful advice

Now the question. It is a 2002 XJS with the 4.0 V8 mfg 10/01, 73,000 miles so it should have the gen II tensioners. Should I change them to the gen IIIs? Is it possible that the left bank tensioner bled down and the cam timing was off just enough to cause the really low compression?

Thanks again

Jim

 

There have been reports of cracks in the bodies of gen 2, but I don't think any failures. If it were mine I would change them. A loss of pressure in the tensioner would likely result in a rattle from the chain, but a slight change in timing will not cause compression loss. If the cam skipped a couple of teeth you would have bent valves and 0 compression, and it would not get better.

 

Have you rechecked compression - I don't like the 5 psi.

ps I did tell you to run away after starting!

 

I have not rechecked compression but the engine runs too good for there to be a serious problem. No blow by, missing etc. I am going to look into the Gen III tensioners for the secondary timing chain. Where do you suggest getting the parts and service information / service manual pages etc. for this project?

Jim

 

Have a look in the ten thousand tensioner threads for US recommendations - I believe you can use Ford parts.