A third Jag has just entered the current stable (the prowl?), a new to me 86 XJ6, so here I am wandering into the XJ area of J-L…
It needs some attention but is fairly well-sorted.
I’m looking for a good factory type service manual, preferably a digital version? What’s the best source for this? Link? If digital lacks content found in print, please advise. Thank you all in advance!
Mike,
Welcome!
In addition to the green and white owners manuals what you need for a Series III XJ6
is the Service Manual, the Parts Catalogue, and the S57 Electrical Guide.
I don’t believe in the digital versions and only have the hard copies that I purchased on eBay over 20 years ago. Someone else will have to address the digital stuff, which I understand has built in security features that don’t stand the test of time like hard copies do.
Paul
The MOST work I have to do on any new project car is reversing or sorting out problems created by other’s “repairs”…
There’s no vacuum hose connected to the vacuum capsule on the distributor. I assume there should be one? It’s not clear to me from the pdf manual (or I just failed to find the info) how exactly the vac lines are supposed to be routed for the distributor. Apparently there’s a gadget or two involved as well. Really could use some detailed diagram or insight. There are dried out crumbling hoses and missing hoses (evident from empty fittings which are now vacuum leaks)
This is for an '85. Your '86 should be the same.
https://www.jag-lovers.org/xjlovers/xjfaq/vacuum.htm
Also search archives for “vacuum regulator”
Cheers
DD
Having the correct search term was key! Thank you, now I understand how this works.
Mike,
You won’t find the vacuum hose information in the Electrical Guide but you will find it in the decals located on the underside of the hood (bonnet) of your car. Some of those decals are circled on the attached picture of the hood of my former 1984 XJ6 Vanden Plas.
Emissions systems varied over the years and from country to country so using the information on your hood is best, unless the decals have been damaged or removed.
It is common to have those hoses missing or misrouted and components missing especially if the cylinder head has been removed and replaced by someone that didn’t know what they were doing.
You will find lots of posts about this in the archives if you search for “vacuum hoses” or “vacuum regulator”.
Paul
Does anyone know what, if anything, is different about the US cars to need the vacuum regulator gadget? I’ve done all the recommended reading.
Other countries used it as well. It’s an emission control device, in essence. Primarily to reduce NOX, I reckon
Cheers
DD
Crudely; ‘US’ traditionally used ‘ported’ vacuum for distributor, Mike - later basically related to emission control. While ‘European’, with no emission control requirements, used ‘manifold’ vacuum for max power. As Paul says; your set-up is likely covered on the decals described - but POs may indeed have bastardised the set-up…
Either set-up will run the engine, (it’s the same engine, with the same timing requirements), but the ‘ported’ vacuum usually needs some extra gadgets fitted between source and dist to make the set-up work correctly. The ‘manifold’ set-up simply connects dist directly to manifold vacuum - and the two uses different initial advance settings. Mixing the two won’t work…
To identify source; in idle, ‘manifold’ vacuum reads manifold vacuum - ‘ported’ vacuum reads around ‘0’…
Frank
xj6 85 Sov Europe (UK/NZ)
My 86 XJ6 has a ballast resistor. I have read the threads on this topic, and understand it seems to be a mystery why some series 3 have it and some do not.
I’d like to keep the resistor in the circuit, as it appears this is the stock configuration from the looks of the wiring, on my car at least, and I’d rather not experiment with it. One of the terminals on the resistor it is a bit loose, so it’s just a matter of time and vibration…
Where can I source a spare?
The resistor may have markings denoting resistance and wattage, Mike…
Otherwise; measure the resistance, and it’s likely a ceramic to stand the heat (wattage). It may be available at a radio shack/electronics provider -bb or search the web…
As it is a permanent inline resistor; if it fails - just connect the white directly to coil positive.
Frank
xj6 85 Sov Europe (UK/NZ)
Your '86 should have the resistor, which lives under a tin shield, attached directly to the coil. This was the set-up used after VIN 421xxx
I’ve never seen the resistor available as a individual replacement part. You bought a coil and the resistor came with it.
It might take some searching to find a new coil with the resistor. From memory (ha ha) the coils were made by Ducellier and carried a Jaguar number of DAC3001 or DBC1140
I’d go with Frank’s advice
Cheers
DD
I got a digital version of the manual which is fine except for the electrical circuit diagrams.
My voltmeter doesn’t move (stuck around 12) and the battery warning light is always on. Yes, the alternator is charging. Actual voltage is mid 13’s, while the gauge and warning indicate otherwise.
So I am in need of a legible schematic to troubleshoot why my meter and light aren’t reflecting the actual situation.
The electrical schematics for a Series III XJ6 can be found in the Series III Service Manual, the Series III S-57 Electrical Guide and the Series III Electrical Wiring Diagram that originally came with the car. These can all be found on eBay or through a variety of vendors. There are also a variety of aftermarket products available.
Paul
Check that the volt meter is getting the 13+ volts on the green wire and make sure the volt meter has a good ground on the black wire. If those checks are OK then the meter itself is suspect.
For the warning light check the brown/black wire at the back of the alternator. It should have continuity all the way to the warning light and, of course, not be grounded along the way…which is what I suspect has happened.
I should’ve asked if the warning light stays on dimly or brightly. If dimly, the alternator diode pack is suspect.
Cheers
DD
If the dash volt meter is stuck at 12V even with ign ‘off’; it’s defective, of course, Mike. The brown/black wire mentioned by Doug grounds the lamp through the alternator when not running - it sometimes disconnects from alt and may short to ground. To check diodes; disconnect a battery post and measure current between post and clamp - normally some 30mA, faulty diodes will give very high current leak…
When you get the wiring diagrams; look for two different faults.
Frank
xj6 85 Sov Europe (UK/NZ)
I should have stated (or perhaps observed) more clearly - the dash volt meter moves, it just reads low. Whether it’s just obstructed internally at about 12, that I can not be sure until I check the wires suggested by Doug.
The alternator seems really difficult to access (?), so I could not find the brown/black wire.
For now, I plugged a digital voltmeter into the cigarette lighter socket, and found a PDF online for 87~88. 
You can adjust the volt meter, there is an adjusting screw behind, all you need is to measure battery voltage and make it read the same. Mind you, it’s a thermal device so it needs some time to move and stabilise.
Mike,
before getting into bigger projects I’d start with the simple things, notably the connectors in the engine bay. They may be corroded. Undo them and sand, clean and lubricate the contacts. Even if it doesn’t solve your problems it’s good practice and cheap insurance against future failures.
If the problem remains, I’d care about the contacts at the instrument. Undo the large guage adjacent, then reach in and undo the voltmeter.
If the problem remains, check the voltmeter against your DMM and adjust, if possible.
Good luck
Jochen
75 XJ6L 4.2 auto (UK spec)
Great info, thanks all!
Does the brown/black wire run down the right side wing then across? Some of the wiring seems to disappear then appear again. I’m unsure how the harnesses are routed.
