Warrjon, I suppose I will have to contact the company to find out which unit I will need.
Thanks for the help.
Cheers, RagJag

 

Have you given up on fixing what you have?

Someone pointed out that there are four pieces to the cruise control system, the dump valve, the vacuum pump, the bellows and the computer.

Each part can be found on eBay for less than $30. It may be cheaper to fix what you have.

I'll keep you posted when I find the problem part with my setup. The bellows holds a vacuum, and the dump valve was replaced. I'm now looking to replace the vacuum pump. It appears Land Rovers and Volvo's used the same vacuum pump, so it's not gonna cost too much.

If I find out it's the pump, I'll probably end up opening the old part up. To see if it could have been fixed. I'll make sure to report back here.

 

Thanks Vee. If you are able to get your cruise control, do let us know.
RagJag.

 

I've just purchased a vacuum pump for $17, shipped.

The dump valve I purchased was $19, also shipped. (Which did not resolve my issue)

I'll let you know how it goes.

If it doesn't work, the only thing left would be the brain.

 

Strike Two!

I replaced the pump with the one I bought and still no cruise control.

It could be the brain, but I don't know if I want to throw anymore parts at this problem for now.

I will play around with the old pump and see if it really was at fault.

The two tubes feeding the vacuum look good... I can't figure out the problem!

I will check out the brake switch too.

 

You can just apply 12v to the pump and see if you get vacuum. It is not a lot but is definite. Same with the dump valve, suck on it and it should not leak unless you apply 12v, or remove, not sure which way it worked. My brain unit was faulty as the got well had got a bunch of water in it some time. Oppenheimer brain unit and all the tracks were corroded beyond repair. EBay helped. Was same unit as from xj6.

 

Hi all, I have read this thread many times and checked all the things I could on my '96 XJS. I was intrigued with the manual test of the vacuum motor. I did this with a cheap hand vacuum pump from Harbor Ft. and a motorcycle 12v battery. The pump was drawing about 2 psi but would only hold that when I pinched off the dump valve line. I thought this is it. So I bought a used dump valve on Ebay for $15, switched them out and on the road I went. Holding my breath, I engaged the cruise and LORD ALMIGHTY I have cruise. This simple test saved me a new switch, actuator motor and many hours of futile labor. Try it. Thanks to all of you who contributed to this thread. This is my first entry but hope to contribute as I can.

 

Warrjon, Are you still out there trying to fix your cruise? I bought the Rostra cruise control unit and found that there is very limited room under the bonnet to mount the box. I may be able to put it on the passenger side by moving the drain hose from the wiper well on that side. Not sure I can even do that.
Cheers, RagJag

 

All great information! Thanks.

 

I have fitted one recently (!).
I sited it in the wheelarch behind the baffle at the cabin end.

The actaution cable used the grommet that the huge loom cable has to enter the engine bay. Mine being a RHD car, but using the Left side would be the same. The unit was mounted upright. I made a hole through to the cabin for the Rostra loom just below the OEM bulkhead connector plugs.