XJSC not started since 1994 - not turning when manually turned at crank


I am a newbie here and also to the intricacies of the XJSC.
My XJSC has been parked up and not started since 1994 and with the CV lockdown I have finally had some time to start looking at it.
I took a chance and stuck a new battery on turned key to see if it would turn over but just a strong click from the starter motor area and nothing turned.

I did some reading and removed the AC compressor and cruise control bellow and took all 12 plugs out and poured Marvel Mystery oil into the piston chambers. I got 11 out first time and then left for 3 days and then took last one out and left that one a couple of hours and tried to turn manually by the crankshaft bolt. But it was absolutely stuck and would not budge.

I do not know if I need to give the last cylinder time soak and try again or if I have major engine problems.

I am getting the welding and bodywork done on the car and a few guys from the industrial estate have been tuning in. One said the engine is seized and it needs to be replaced. The second guy said I need to take the engine out and get it overhauled as there may be common faults that need to be rectified and that whilst it is out, all looms can be checked and gearbox and clutch plates checked and also engine bay checked and sprayed. The third guy said, just buy a second hand engine and put that. My immediate thought was the fear of getting an engine that might fail shortly after installation which would be disastrous.

I am clueless as to what is best. I just want the option that will last and give me (hopefully) the least amount of problems later down the line.

If the second option is the best, is there anyone who I can take the engine to for it to be overhauled?

Many thanks


The choice is yours, but I’ll point out a couple of factors:

  1. Getting this engine – or any Jaguar V12 engine – rebuilt by an expert will be staggeringly expensive. Most on this forum would do it ourselves rather than pay someone; it’s much cheaper to DIY.

  2. Getting a second-hand engine, OTOH, can be astoundingly cheap. In fact, play your cards right, you might even pick one up for free. People use them as boat anchors and coffee tables. Yeah, you wouldn’t know what’s wrong with it, but really you don’t know what all is wrong with the one you have, either.

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Hi Kirbert

Thank you for taking the time to reply and for making those points.

I would love to do a DIY job but apart from taking motor vehicle engineering at school 30 odd years ago, I would not know where to start.

I am very hands on and love a project and have built up a few tools to get me this far.

Are there any key aspects of the engine that I should address doing it myself and are there any sources of information in relation to doing that work and the torque settings in re-assembly?



I wrote a whole book on it. Rebuild of this engine is not difficult, just time consuming, and the amount of cash you’ll save doing it yourself will easily pay for any tools you need.

One word of warning: If you use an engine stand – as is recommended – you’ll need the heftiest one you can find. This engine is heavier than most V8’s and it’s also longer, hanging the weight waaaay out front on the stand.

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Dear Kirbert

Thank you for this and I hadn’t realised that I was in the presence of greatness!

The book is unbelievable (I only managed skimmed the engine work section very quickly).

I think I have 2 problems: 1. not knowing what to target; and 2. not knowing if something is wrong and needs replacing/reworking eg valve seating issues.

Is there a checklist of must change/replace items and/ jobs that should be done as a matter of course or is it a case of taking everything off and replacing all/some parts when re-assembling?



Since you removed the plugs and added the MMO have you tried the started?


We just call’im “His Kirbness.”


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OBYH what direction did you try to turn crank, both?

I turned clockwise as I read that turning anti clockwise might mess up the tensioners. But I tried rocking it clockwise and anti clockwise but it was stuck solid. I am going to try again tomorrow to see if marvel mystery has done anything. I’ve done a few more YouTube videos and have got some seafoam deep creep lubricant coming so will try that as a last resort.

You start a thread, you post pictures, you ask questions and I’m sure you will get lots of help and guidance here. There are quite a few people of greatness in this forum.

Rebuilding a Jaguar V12 engine might have some peculiarities, but it’s an engine like any other.
IMHO, there are two difficult jobs:
Taking the engine out, but this you might have to do anyway…
Taking the heads of.

First see if you can turn the engine over, then measure compression, do a leak down test and report back.
This will determine your next steps.


Aristides I right. this is pretty much what I have done and I have received a bunch of very helpful information from a ton of knowledgeable people. I’ll try and give you some pointers here and there too, as Its still very fresh in my mind. I am currently assembling my V12.

Thank you very much.

I will get it turning and then run the compression and leak down tests and post the results.


These are some pictures I took of the plugs as they came out.

I am not sure if anyone can make any findings from the plugs…

It’s always a good practice, before plug removal, to reach down with an extended blowgun, and blow the crud out of the plug wells.

A couple of the electrodes show evidence of moisture.

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Thanks Paul

Believe it or not I blew and vacuumed around the plugs and plugs area extensively but the crud build up was horrendous. I did more cleaning once plugs were out being careful that none fell in through the spark plug hole. So the new NGKs will have a nice clean home to go in to.
Is there anything you can tell me about the way the engine was running from the condition of the spark plugs?



Hi all

I have good news and a bit of bad news…

I spoke to a mechanic and he asked if I had removed the belts from the crank as it might not be the pistons being stuck. I had already removed the belt connected to the AC compressor to get to A1 and B1 so I cut the belt second in from the bumper side. I think it operates the power steering pump and it pulls another wheel and I do not know what that is.

I went to manually turn the engine and it turned! I can’t really explain the level of ecstasy when it turned having tried all sorts to turn it.

With that, I had key in hand and immediately went to the ignition hoping to hear the sound of the stater motor turning the engine but it wasn’t to be. All I got was a click as before. So ecstasy soon turned to disappointment as I looked at the beast in the engine bay, willing it to give me something…anything.

So overall I am in a more positive place than I was before but does anyone have any suggestions as to what it could be.

I have removed the coil when I was doing the plugs, I am wondering if this needs reconnecting or if I am looking at a starter motor replacement. Or if there is something fundamental that I am doing wrong.

Many thanks in anticipation


Not really: about that can be said is, it appears it was running not too rich nor too lean.

Time to begin with basics:
-is the battery good, as in, has it been charged and load tested?
-are the cables and posts clean?
-is the solenoid being energized with a full 12 volts?

Thank you:

  1. Brand new Yuasa (attaches)
  2. cables and posts are clean
  3. Now I do not know what the solenoid is but I will youtube it. Do I just run a volt meter across it when ignition is turned to on position when lights come on?

I will try and post a link to video footage of me turning key and the warning light that cane in and the sound of the click. There is the sound of a car in the background but this is not the XJSC