XJ12 recommissioning

I’ve gone off-piste with this one.
Usually I go for simple cars, roll up or even no windows. No exterior door handles is good. Lack of complexity makes it easier to restore/maintain an old car.
But I’ve loved XJ6s since I was a teenager. They’re just so gorgeous.
And when I saw a picture of one in my preferred colour combo, it was love.
So I made plans to drive the 6 hours to look at/buy it. Had a mate teed up to come and drive it home.
But then I remembered a car that an old guy had offered me about 5 years ago. An XJ12.
And they say you should own a V12 once in your life, so it was easy to justify even more complexity with a lower entry price and a much, much closer pick up. I had to ring and cancel the love at first sight one.

So I’ve brought this home.

It needs serious recommissioning just to get it drivable. If I can get it past that hurdle, I’ll drive it a bit, and decide if it’s worthwhile doing a more thorough resto.

Started with the fuel side of things. It hasn’t run for 5 years or more, so dried up fuel will have to be sorted.

The filler neck of both tanks was enough to tell me the tanks would need removing and rust repairs would be just a question of degree.

So off with the back bumper and lower rear valence on each side.

The valences had been off before, evidenced by the assortment of washers.

What do these people do? Throw the fasteners from all jobs in a bucket and then select ones that are ‘close enough’ when reassembling?

It took most of the day to get both tanks out, but I am chuffed with what I’ve found. The tanks will need cleaning but seem to be in excellent condition. As is the rear of the car. No rust found other than a pinhole in the spare tyre well. Hasn’t yet been cleaned in this photo.


The area occupied by the tanks is thankfully rust and damage free, both sides.


One of the tanks. That’s the drain on the bottom left of the photo. About 3 cups of dried up fuel flakes came out of each tank. Not sure how I’ll clean these yet.


Was also very pleased that all the fasteners came out with no trouble. Nice in a 50 year old car.

Next will be to flush the fuel lines an see if the pumps work, then carbs.

Thanks in anticipation of advice to come.

3 Likes

looks good,
what part of Aus are you

Ask and thou shall be given, Garry…:slight_smile:

Being carbed it is likely thirsty, but generally ‘easier’ to get running. I trust you have run a compression test as a precaution…?

Frank
xj6 85 Sov Europe (UK/NZ)

Thanks Tom,
Tamworth NSW
You?

No compression test yet.
I’m going to remove the plugs to put some oil in the cylinders, so I might check it then.
Cheers

just down the road nth west sydney

There is no ‘might’ about it, Garry; while a convenient occasion; the compression test is the important one - revealing the general state of the engine…

The 'dry’test , without oil, will reveal any valve or gasket faults. The ‘wet’ test, adding a spoonful of engine oil to each cylinder, will also reveal the degree of bore/ring wear by the raising compression on relevant cylinders - but will not mask valve or gasket faults…

As the evenness rather than the actual pressure is the important bit, use consistent procedure for each cylinder; floor the pedal and crank for four seconds. And write down the result for each cylinder - do not rely on memory…:slight_smile:

Frank
xj6 85 Sov Europe (UK/NZ)

1 Like

I checked the tanks this morning and it appears the molasses is working. So I plugged all the holes in one tank except the filler neck and topped it up with the magical mix. What can’t this stuff do? My wife even makes a delicious pear and molasses cake!
I’ve flushed out the lines around the fuel pumps and tried the pumps by hooking them direct to a battery but no luck.
Removed one pump and marked it so I could put it back together.

A parts book and a repair manual came with the car, so I approached this pretty confidently. But forgot to take any progress pics.

Pulled it apart and cleaned it. Diaphragms were ok. Had to make a couple of new gaskets and reassembled it. Tried it on the battery and both sides worked. Well the points clicked and the diaphragm moved. So hopefully it will pump fuel.

And once reinstalled, and hooked up to a temporary supply, it did.

I think the problem was mostly the plunger shaft sticking, there wasn’t any real gumminess in the diaphragm, so I might just take the points cover off the next one. If that works it’ll save me making gaskets.


That’s a pic of the points end of the pump. Which I can’t get to work. I tried it without separating the valve body from the electromagnet end, in order to not disturb the diaphragm. It will pull the plunger in once each time I make contact, but won’t do the make and break thing.
So I took those screws out and got one side of it to cycle in and out, but the other side wouldn’t cooperate. All I’ve worked out so far is that one capacitor has no continuity, so I think that’s going to be the problem.

Also have to look at the fuel gauge senders. Both of them were seized, which made getting them out of the tanks difficult. They look pretty bad.


Thanks.

1 Like

Does it actually break the current to allow the spring to return the plunger, Gerry? If powered, the spring cannot ‘retract’ - and a faulty/binding spring/plunger cannot retract…

On the pump stroke, one-way valve is closed, on the return stroke valve is open to refill. The adjustments/clearances on the contact fingers are small and critical and may required bending, or other available adjustments, to get the repeat pump stroke. Ie reconnect the power. I trust the contact are all clean and connected. Ohming or a test lamp may give clues?

Usually the pump also stops pumping when the back pressure from carb reaches the designed, usually adjustable, pressure. Which makes it more complicated.

Frank
xj6 85 Sov Europe (UK/NZ)

Just saying, thanks for teaching me…I would have…first thing…checked oil…then gravity fed the carbs with fuel from a gas can tapped to the windshield (actually a large funnel filled with fuel, taped)…but now I have learned to do a dry compression test first…then wet…then gravity fed.
Why, because if the engine is bad…then the escapade (adventure) is over
Anyway…thanks for teaching.me…Frank
Mitch
Oh…and once the adventure is over…the engine bad…parts go in the trunk…now apart the project is worth a whole lot less…that is why
Blast from the past…I am 10 years old circa '1967 GMAC repo lot, Chicago…big black kind hearted yard guy teaches me…with american V8’s undo wing nut on air cleaner…pour fuel into recess and crank…start…just need to loosen wing nut and short fat jumper cables from battery on dolly…thousands and thousands of cars latter…still going/learning

One more feature to that well knw first start. Fill the csrb bowls through the vent tubes. Teh engine should run if all ese is OK.

CHJ

That compression is ‘good’ doesn’t really mean that there are no faults, Gerry - only that there is nothing wrong ‘upstairs’; but the ‘bottom’ of the V12 is almost bulletproof…so…:slight_smile:

You can run the test with all plugs removed, but with the ‘wet’ test it will be a bit messy, oil tends to spray out - so throw a cover of engine while doing that. The important thing is to do all the cylinders under the same conditions - and write down the result…:slight_smile:

Frank
xj6 85 Sov Europe (UK/NZ)

Well I got the pump to work. Proving that I didn’t understand the circuit. It was the points. Pulled them out and sanded/filed them and all is good. One side of the pump cycles much faster than the other and all I can put that down to is the stiffness of the diaphragms. I’ll keep an eye on them when/if I get the car running. I’m a bit in awe of the complexity of this part of the fuel system. Two tanks, two sender units, two double pumps and two solenoid valves. And about 3 metres of hose plus twenty or more clamps.

The spare tyre well after a scrub and the fuel bits mostly in place.
There’s a bit of surface rust and one pinhole. I’m not sure what to use on the rust both here and under the guards where the fuel tanks go. Suggestions very welcome.

I’ve ordered some rebuild kits for the carbs. The rotary throttle bizzo on top of the motor ( circled ) won’t turn


Because the carb butterflies are pretty much locked. The carbs look like this.

Don’t know what that sticky green tinge is. Maybe evaporated fuel?

While I wait for the carb kits and the molasses in the tanks, I’ve removed the radiator.
First step, remove the bonnet. Quite easy really, half a dozen bolts. A bit disappointed in the Jag engineering team.


Radiator will go to a specialist for a clean out. It looks to be in good order, and I was pleased to see a touch of green in the coolant that was released.

And I put a socket on the crank bolt and was very relieved when it turned. I only moved it about a zillionth of a degree, haven’t put any oil down the bores yet. Just enough to see that it’s not frozen.

Thanks

1 Like

Garry,

looks like you are really lucky with this car! As regards the spare wheel well I’d proceed conservatively: clean, remove surface rust, put on converter, then seal with a paint close to your original colour.

Cleaning the carbs may be more involving. Again, I 'd try not to disturb more components than necessary. Start with the butterfly and the shaft. Remove the remainders of fuel with brake cleaner or some kind of solvent.

As for the main component fasteners Jaguar were meticulous. I’m still surprised that after always 50 years the bolts will come off and remain in good shape. In stark contrast, Jaguar seems to have used tin screws from a big bin, whatever was available.

Good luck

Jochen

75 XJ6L 4.2 auto (UK spec)

This is a perpetual discussion when an engine is ‘recommissioned’, Garry…:slight_smile:

How much preparation before the engine is cranked. And rotating the engine manually and is of course a wise precaution. If ot cannot turn the engine manually, with reasonable force some thinking is called for. Brute force may be seriously damaging - but it may also be a good solution…

There is no disagreement as to changing of all liquids before using the car - but to what extent it is required before actually starting the car first time or getting it running, can be argued. A running engine is a sort of proof of the pudding; you have ‘something’ working with minimal investment - but at some risk…
.
There are no pat solutions, but an engine spinning on the starter is a necessity for further assessment or work on a project…

Frank
xj6 85 Sov Europe (UK/NZ)

Not much photo worthy today.

Degreased the front of the engine.

Removed the air pump, which didn’t have a pulley on it. That will get rid of a few pipes/hoses.

Also removed the ac compressor and condenser. More hoses gone. The compressor didn’t have a belt on, so I’m assuming it had problems. I can live without ac on this car.

Pulled the spark plugs one at a time. Was very careful, blowing any water/crud from around them several times as I unscrewed them. Then cleaned the threads, started them in the hole and blew around them yet again. Then took them back out and lubed the threads.

Before screwing them back in, I sprayed some oil in the cylinder using the wand from a spray can of chassis rust treatment. This has a circular atomiser on the end - ensures that the oil gets everywhere. This took an age, with a dozen plugs to do.

Then I turned the engine over several times by hand. So I think I’ve appeased the relevant engine gods there.

I did take a photo of the fuel tank filler necks that bolt to the body.

During the cleaning. Bead blaster is an excellent thing.


Tomorrow I might put a battery in it and spin the engine on the starter and see if it has oil pressure.

Thanks

5 Likes

Looks gorgeous! Only surface rust and even a clean surface after the blasting! What do you do to keep it that way? The tin part can be primed and painted, but the hinge part seems difficult to me.

Good luck

Jochen

75 XJ6L 4.2 auto (UK spec)

Thanks Jochen,
I think it will be ok as is, but if the steel flap does rust, I’ll take it out again (easy) and nickel plate it.

Didn’t get a battery, so didn’t turn the motor over. Maybe tomorrow.

I moved the molasses from one, hopefully clean tank to the other.
Then I got the cement mixer out and strapped a couple of pieces of 6x2 on the business end, then strapped the empty tank to that. Easier said than done, I might add.

Then emptied a four litre tin of vibrating media ( think pea sized gravel ) into the tank along with about 5 litres of diluted hydrochloric acid and let it spin for probably half an hour.

Drained the acid/media and put some soapy water in. There was still some media left in it.

Scrubbed up nicely. Once I’d flushed out the soapy water and media, I took it off the machine and put some diluted Deoxit ( phosphoric ) and sloshed it around. Then dried it with a heat gun, to keep flash rust to a minimum.

It was then that I saw there was still some fuel residue in the bottom seam. So now I’ve got it standing up with a few litres of molasses in the bottom, just to get the last of it.

The front of the engine is almost clean. I’ve ordered a set of rad hoses, when they arrive and the rad is cleaned, it can all go back together.

A bit closer, still some cleaning to do. Access will never be this good!

Thanks.

3 Likes

And of course you’ll be changing all belts and hoses that are accessible now! Just be sure to get good quality …

Good luck

Jochen

75 XJ6L 4.2 auto (UK spec)

1 Like