Hi Trevor have never seen a 3.6 with Cruise Control I would have thought the car would need to be Automatic to start with,
The V12’s all had it but initially it was proven to be lethal. I was coming off a motor way in the early days 1986/7 and it would not cut out when I hit the brakes quite hair raising & frightening, Jaguar all but called me a liar and said it was not possible. Just a few months later there was a re-call after someone had been killed.
There is nothing in the parts book re parts for 3.6 cruise control.
Pleased to see you are still with us Trevor from around 2011.

The facelift 4.0 litre models do have Cruise Control as an option< so you might be able to retro fit one to your 3.6 Automatic Trevor. I have a donor 1995 4.0litre XJS auto, with Cruise Control, which at some point in the future I'm hoping to dismantle and reassemble in either my 1994 Couple or possibly the 1993 Convertible - all something for the future at the moment I'm afraid. Laurence

Hi Trevor, Cruise was indeed an option on 3.6l XJS both cabriolet and coupe. The earlier system was AE Econocruise but in Feb 1987 was replaced with the more sophisticated Hella ‘computer’ cruise. (Source Skilleter – says vin 108285 roughly)
Same 1987.5 model year revamp they introduced wood veneered ski-slope.

If yours is a 1987 it might be quite straightforward..

The system is however a little more complex than you might think at first sight but I believe should be retrofitable to cars post Feb 1987. I don’t think anyone would recommend the Econocruise version but the Hella by all accounts is a reliable and sophisticated system.

Components:
Ski-slope switch & mounting, ECU which fits under passenger foot board next to main 3.6l engine ECU, brake pedal actuating double switch (and single clutch switch on manual cars), solenoid vacuum valve fits on N/S inside engine bulkhead, Actuator bellows, tubing and linkage to throttle.
I haven’t mentioned wiring or relays either but I think will be already in harness on post 1987 cars. I cannot confirm that but my Sept 1987 certainly has an extra plug in footwell next to location for the cruise ECU.

The 3.6l (& 4.0l) models use a totally different system to that on the V12 cars so no major components are the same (happy to be corrected)

My own cab does not have cruise but I have slowly been gathering the required components myself for future fitting. The ECU latest version is cheap enough at circa £20 brand new off eBay, console switches quite costly as are the bellows as often second hand ones look poor. Double brake pedal switches (cruise and brake light) are more difficult to find but I’m sure if you approached one of the known Jag breakers like ‘JustXJS’ at Derby they could source all the necessary parts.
The parts aren’t really that costly.
The missing ingredient is whether the existing wiring loom has the connections already there and I cannot confirm that myself yet..

If anyone has actually done the modification on a post 1987 I would also be most interested to hear of any pitfalls..

Regards, Robin

Parts References for 3.6l Cruise Control – poor pics but shows where to get the info!

If it works well then could be a good option. I imagine will be similar to the Jag ‘Econocruise’ early system which was also an aftermarket fitment originally, before being offered by Jaguar as an option in production.

Modern electronics might have benefits too.

Let us know how you get on if you go that route, be most interested.

Regards, Robin

Hi Trevor

Any update to share on your Cruise Control install ?

Laurence

Interesting about the Cruise Control not fitted on the 3.6 Auto, as posted by Bleasie further up. Ours has it!!!!

Well Jon you know what they say you learn something every day.

Hi Trevor,

If it means you can be comfortable driving your Cabriolet the distances you do, then it will be a great success.

Enjoy your tour around Ireland

Laurence

Just as an aside to all this, the 85 Cab has a crude mechanical/vacuum system. I scrapped mine long ago, its ok when new, but not good as it ages.
The tiny brass strip flap valves don’t seal any more and speed can’t be held.
Of course these tiny bits can’t be bought so you’re faced with buying the complete unit – if you can find one.
Anyway, taking the big vacuum cylinder out means more airflow across the engine which is good.

That’s great news Trevor, really pleased about that news.

Wish I had time to go on a few day/week tour in one of our XJS, but have to restrict it to annaul holidays or long bank holiday weekends for now.

Laurence

many moons ago i test drove a 3.6 manual coupe (complete shed) and im sure it had cruise control. there was a stalk on the left side of the steering column, didnt think to see if it was cruise but cant think what else it could have been. As soon as i saw the car I wasnt interested as in my opinion it was a parts car

Interested in what Richard Salt refers to as “the crude mechanical/vacuum system”, are you refering to the V12 ?

Do we mind if we expand the discussion to the V12 vacuum system ? My CC doesn’t function but its not important to me so I haven’t looked at it yet. On the other hand I do like all parts of a car to function properly so maybe this will trigger me to action ! I am hands on.

So Richard please let me/us in to the secret, where are these “tiny brass strip flap valves” and the “big vacuum cylinder” too please.

Many thanks