Thanks.

What is inertia switch and where is it located? Is it better to disconnect inertia switch instead of fuel pump relay?

 

The inertia switch is the black box by your left knee on the door hinge area (the A pillar as called). You should see a round button-like thing in the top which gets triggered (I forget whether up of down, but the opposite of what it is now) in the event of a collision and cuts the fuel pump. Safest to do BOTH, disconnect fuel pump and switch.
Greg

 

Spent most of the day today getting into the Vee and to spark plugs in order to perform the compression test.

I was able to get to all plugs except #5 cylinder. No matter how I looked and looked, I just could not get to the plug with the throttle pedestal on. And I was not brave enough to start dismantling everything around the throttle pedestal (though I did some dismantling). Those two back bolts looked awfully scary. Virtually inaccessible.

So, I decided to run the test on the 10 cylinders that I did have access too: #1 through #4 and #6.

The results are in (averages of the two tries):


_______ #01 #02 #03 #04 #05 #06
A-bank: 146 140 138 144 ? 140
B-bank: 135 137 __0 136 ? __0


I just realized that I completely forgot to max the throttle when I was cranking the engine. Plus the engine was fairly cold (it is below freezing here today.) That's probably why results were a bit on low side.

But the main news, of course, is two daughnuts on the B-Bank: #3 and #6. I retested a few times just to make sure: still zeros.

Bad news?

 

good work, i'm still saying dropped seats!

the B bank HE engines that have dropped, does run at a hotter temp especially at the rear cylinders!

so that should answer your question!! have fun, also that is precisely why some of these V12 are just given away or recylcled.

i had two given to me just to get them off the property, 1975 XJ12C coupe, and 1978 XJS V12 , free NO charge!

 

I still don't know what #5 looks like. But I guess at this point it does not matter much

So, zero reading is a sign of the dropped valve seat? No pressure at all?

 

Sadly, yes.

Wasting time now to just find out the other 2 would make no difference.

That engine is coming out, both heads off, get them tested for hardness, then do the seats etc properly, visual the piston tops for damage (not common), reassemble and drive on.

 

Big decision: if you really want a good XJS redo the thing. Engine out is hard work but quite doable if you have a garage or similar to work in. Lots of other bits that will soon fail can be renewed at the same time, and it will take minutes instead of hours a access problems disappear once the engine is out. Think it over carefully, a bits budget of 1500 USD would be absolute tops, probably quite a bit less if the studs etc are OK, and the valves just need a clean and fettle. If the head is toast, second hand ones are out there. Got to be your hobby though, not feel like a job of work. A bit like the right girl, you seem to be able to not be driven mad by them, in spite of all!
Greg

 

Thanks, all. Yes, that's why I got into xjs -- wanted a hobby that is completely different from my day job. And I really liked the "classiness" of XJS.

Need to think a bit to reassess the situation. Some folks say one could get another XJS on a cheap. (I got mine this way too.) Maybe something falls into my lap and I can have two cars from which to build together one good running. Chevy conversion is also a possibility, but so far it is not my preferred option. Need to think...

Ok, while I am putting everything back together, should I maybe just not connect the leads to B3 and B6 at all? And also disconnect the B3 and B6 injectors? Would it help me continue to run some other tests in the garage (as I keep learning more and more about XJS) without further damaging the engine? (This way at least neither fuel nor sparks will be getting into B3 and B6, correct?)

 

Forget it as far as keeping it going in this concerned, nothing but further damage will be done. No other tests needed. A V8 conversion will be the most expensive option, but another XJS might be viable using the current car as a parts source, but will not be cheaper than an engine repair, assuming say even as low as 3000 for a decent car. Also remember, not all XJSs are the same, you need two cars that are the same age/spec.
If you do get stuck in to the repair, I guarantee you will have a huge feeling of achievement when done. All a matter of what you individually want.
Greg

 

on bank B
remove valve cover....
check valve lash...
the get a plastigage and check the clearance of the cam in the caps...
they should all be the same more wear at the rear would give a similar result..
Mazda and ford... low oil pressure can damage the caps and prevent proper operation of the cams and they only have v6 and v8s'
there is a neat trick that can fix that problem...

 

Understood. What model years would work for me? Mine is '86 (HE), US specs. So, I assume '85 and '87 would work, right? Can this range be extended on either side?

Also, thanks for the encouragement. This is the type of things I envisioned it might come down to. Getting the head off and being able to see the inner working of the engine. It is pretty cool! But it is a commitment. Complication is that my garage is about 200 miles from the place where I stay during work week. So, I only will have weekends and holidays. Still doable, but I would need to be a lot more organized.

 

The HE you seek is from 1983 to late 1988.

Before 83ish is what is known as the preHE, and after 88ish is the Marelli cars.

The Marelli engine can be used, but for a first timer I do not suggest it.

That engine and trans sould be out in about 6 hours of organised and concentrated effort.

With the chance of 2 valve seats dropped, that engine has been seriously overheated, and probably more than once.

The transmission ,TH400 GM unit, will need checking also, as its cooler is inside the radiator, and will have overheated that fluid as well. Probably no damage, but whillst its out, get it checked. Smell the fluid, if it smells BURNT, then maybe some damage, but that TH400 is STRONG.

 

re Car type. The XJS had a semi facelift about 2008. The seats changed to a more "Recaro" type and they do NOT fit the cars produced beforehand without new welded fixings being done on the floorpan. The aircon unit and switchgear also changed, as well as the ignition to Marelli. So if the seats are the same, and the car is an HE (NOT a pre HE) you will be fine.
Greg

 

Greg,

I want TWO of those 2008 XJ-S.

You know my address, so just get on with it maaaaaaate.

 

I will fax a couple today! just tell m your preferred colour...
Greg

 

Got my official XJS repair manual (thick green book) last night. It has a section on how to remove the engine ...

Anyway, if I do decide to undertake this (which would be by far the biggest car-related repair -- I once replaced a gasket on Volvo 760T, but it was straight four 2.4L engine, with plenty of space under the hood. And it was 15 years ago...), what would the $1500 budget be needed for?

Special tools? Engine hoist? All that is included in the $1500? What else?

 

Punt, you dont know the history of the engine and to invest a dollar in to it is foolish. With two dead cylinders, it most likely was seriously over heated or ran very hot for a long time. The chances of the head not being warped and twisted are slim to none. It probably wont even come off the block with out a major fight. Then if you do get the head off, there could be piston and wall damage if a piece of the seat crack off. Then you would need to know you solved the original issue that caused the two dropped valve seats or it will happen again. This scenario is not so far fetched, it's happened where the side of the engine with the temp sensor is fine, the other side overheats and destroys another engine even though the gauge never went above normal. Additionally the chances of a neophyte mechanic pulling off a successful repair on budget with one of the most complex road engines ever installed is highly unlikely.

Your best options as I see it... 1. Source a newer and known good V12 and install it, a big gamble and a monumental task for the inexperienced. 2. Do a conversion. Merits have been discussed at length. 3. Treat this car as a parts car and punt on this XJS and perhaps purchase another that runs well but maybe needs good parts you already have.

 

1987 V12 and tranny in local Craigslist for $1000. Claimed running when pulled for a swap. Been on there for 4 months or so may be possible to negotiate down. No pics currently but when they were up on a previous posting I thought it was actually a pre-HE. If you're interested I'd be glad to get more info for you.

 

Hi v1roc

I agree with icsamerica 150%

What you are thinking of doing is a massive undertaking in the scheme of things, so what do you want to be doing for the Summer, working on an XJS or driving one?

Although that is a decision that only you can make, seeing as you haven't had her very long and maybe not have developed an emotional attachment, which you will when the right XJS comes along.

I think its time for you to cut and run and not Spend another Penny on that Car.

Because of your experience, you are already a lot wiser now so go and spend your money on a nice one you can use and keep the one that you've got now for Parts.

Which I can assure you are worth their weight in gold, because there are a lot of parts that are no longer available and its also very handy to have a Spare Set of Tyres and a Spare Radiator.

Even on a good Car, there will be more than enough work for you to do to bring her up to snuff.

So take your time and money and find yourself a good one that you can use and enjoy and if the Temp Gauge goes over have way, or you hear any strange noises 'Run away'

Also check the rear Rotors, as if they need replacing the IRS needs to come out.

 

I hear you all... I will not dive into it blindly. Regarding the question whether I would rather work on the car or drive the car, the answer is both. This is a hobby. I would like to fix the car so that it runs. But I don't need the wheels. I have three other running cars I use for daily driving.

I kind of agree that waiting for another XJS that would be compatible with mine is probably the best option. I just don't know how long I will have to wait. But it is fine.

In the meantime, I will continue "playing" with this one and use it to learn the quirks and weak points. Just to educate myself and get more expereince.

Really really appreciate everybody's help! I really enjoyed working on this Jag, but it wouldn't be possible without all of your help!