1994 jaguar vander plas xj6 4.0l vacuum schematic
 

https://cimg5.ibsrv.net/gimg/www.jag...c4389aa909.jpg
https://cimg6.ibsrv.net/gimg/www.jag...51d625e0f4.jpg
https://cimg7.ibsrv.net/gimg/www.jag...30f1c6f44c.jpg
https://cimg8.ibsrv.net/gimg/www.jag...900d383580.jpg
Does anyone know what this part is. Itwas located in the engine compartment on the drivers side on the fender by the horn . It has something to do with the vacuum.

Hi Alec

I'm afraid you've posted in the wrong subforum, this is for XJ s from 2003 to 09.

Sorry, but offhand I'm not sure what the correct subforum is for '94.

Dave

Hi Alec,

Welcome to the Jaguar Forums! It's great to have you with us.

I have moved your post from the forum for the X350 to the forum for the XJ40, which is the Jaguar factory project code for your 1994 VDP.

The part in your photos is the Cruise Control Dump Valve. When you press on the brake pedal, it opens to release all the vacuum from the system to immediately disable cruise. It's a critical safety component.

You can easily test the valve. It's normal condition is open, so with no power applied you can blow through it. When you apply 12 volts to the terminals, the valve should close and seal completely so you can no longer blow through it. Failure of the dump valve is a common cause of an inoperative cruise control system.

Please visit the New Member Area - Intro a MUST and post a required introduction so we can learn something about you and your Jaguar and give you a proper welcome.

Cheeers,

Don

Thank you very much. I did a smoke test on my vacuum system and smoke came out of it. My question is, does it stay open when cruise control is off or is suppose to be closed ?

The short answer is that I don't know for sure, but a simple test would be to measure the voltage at the dump valve electrical connector with the engine running (and cruise control off, of course). If you have 12 volts at the connector, the dump valve should be closed. You would think the dump valve should be closed anytime the engine is running but the brake switch is not activated. Otherwise, the dump valve would constitute a constant vacuum leak.

Cheers,

Don

​​​​​​ Run the part number on it. Yes I have one under my purge valve.