My cruise control doesn’t work, any suggestions what might be wrong / not working?

 

Leak check the diaphragm in front of the butterfly shaft tower

Th rubber is getting old

https://www.jaguarforums.com/forum/x...-today-120408/

 

The diaphragm had holes in it but I fixed with bike inner tube repair patches. Where does vacuum come from to work diaphragm. I read it’s electric pump under air filter?

 

Yes ' it's the oval thing under the air filter

 

Have looked over cruise systems. Fuse good, red light comes on when selecting cruise. Vacuum had holes in but have repaired. Blanked dump valve and test drove, still no cruise. Could it be pump ? Can I test with 12 v feed ?

 

There is a CC inhibit if the traction control is commanding the rear wheels to reduce spin rate

Looking into a test procedure since you have the valid light which is good

 

Look at page 91

http://www.jagrepair.com/images/Auto.../jagxj1995.pdf

Your valid light is the LED diode in the cruise control switch pack

A cleaner diagram on the 1996 is on page 104

http://www.jagrepair.com/images/Auto.../jagxj1996.pdf

Is the vacuum pump cylinder body warm to the touch ? It seems to run at all times when CC engaged

Is the hoses attached on the nearby dump valve ?

Anti lock brakes and traction control working along with speedometer working as the speed input is the left rear wheel speed sensor ?

The brake switch from reading gives problems and has been upgraded by a TSB . Can you remove the ground ? This would keep the CC engage in a emergency brake pedal application

http://www.jagrepair.com/images/TSB/...l%20Switch.pdf

There are 2 switches in the assembly , one to run the tail lights

Editing

 

abs, speedo, traction control all working as it should. I blanked dump valve to eliminate. I don’t think vacuum pump runs at all. Can I put 12v feed to pump to see if it runs ?

 

ABS etc working ok. I blanked dump valve to eliminate. Don’t think vacuum pump runs, can I run 12v to it and see if it works?

 

Positive is on the purple / green wire and ground is the blue / yellow wire at the vacuum pump / control valve connector

You can use a battery charger on the low amp setting or pull power from the + terminal post of the LH engine fuse box and there is a ground stud on the chassis rail near the area of interest

 

Battery charger on vacuum pump made a clicking sound but created no vacuum so I guess pump is dead ? How long should bellows hold vacuum. If I squeeze bellows and then place thumb over outlet the bellows open fully in 1-2 seconds. Possibly bellows and pump to replace?

 

The pump may be frozen bearings that may be opened up and physically rotated to free up and reoiled

By the pump twerking by feel in your hands indicates the motor electrical windings are probably intact

Just guessing if that can be done

The diaphragm has a glue around the metal seam that may have become brittle and leaking

 

Good news I got vacuum pump working and creating a vacuum. Blue yellow wire positive, purple green negative. Bellows is U/S so used item on order from e bay.
If I want to test the pump is working on the vehicle should it pump as soon as cruise is turned on or will it only pump when travelling at more than 25mph as that’s min cruise speed ?

 

Try a hilly / changing road

The wiring guide and the breakout sheet page before at 103 on pin 20 for the 1996 is wrong then

I would assume the pump will not turn on until commanded by the switch hence wearing something out when not in use unless the pump has a slow build up time for a quick responce

 

I’m going to jack up the back end and get some one to drive over 25 mph while i check the pump engages when turned on.

 

There is a TSB on running up the engine in park position

I think it has to do with transmission cooling

 

That’s the cruise sorted, bellows replaced and pump freed off.

 

What was that? I have no idea what this means.

 

Vacuum pump had stopped working, so I removed and freed off. Bellows is what vacuum pump controls and so maintains pre selected cruise speed.

 

How did you free up the vacuum pump ?

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