Below are four photos. All the parts are on the righthand side of my 1987 XJ-S V12.

The one labeled "solenoid air switch" has me asking a few questions...where does the hose end go (you can't see it in the photo, but it's cut, and I don't see an obvious "other end". What about the electrical connections?

The photo "vacuum regulator" shows just that. Same deal, the hose on the left is cut right at the device. If I understand the not-very-legible diagram attached to the bonnet, the top right hose goes to a "T", with one end going to the vacuum advance on the distributor, and the other end going to the dump valve?

The other two photos are self-explanatory...I have no idea what they are. "What is this number 1" was below the righthand intake maniford. "What is this number 2" goes into the firewall. Some of the components on the bonnet diagram show a "blue disk", "grey disk" or "red this side", but both of these look to be just black on one side and white on the other.

Any help greatly appreciated!

Thanks,

John
187 XH-S V12, 62,000 miles

 

#1 is the Extra Air Valve. The nipple goes into a grommet on the backside of the RH air filter houisng

#2 Is the vacuum regulator for the vacuum advance, yes. The capped-off nipple should go to the vacuum control valve (I think) which is on the RH water rail (I think). memory a bit foggy on some of this

#3 Looks like a delay valve for the vac advance or air injector?

#4 Perhaps the vacuum check valve for the climate control?

Cheers
DD

 

Oh, on #1 I think the hose end goes to a nipple on the underside of the inlet manifold..or perhaps underside of the throttle body

Cheers
DD

 

Hey Thanks Doug for the response!

Upon closer examination, item #3 has (below the grease and dirt) some printing. On the white side it says DIST, on the black side CARB and also MADE IN THE USA.

When I attache a vacuum gauge to the CARB side, and then suck on the DIST side, when I release the vacuum the gage slowly goes back to zero.

When I attach the gague to the DIST side, and then suck and release on the CARB side, the gauge very quickly drops to zero. It's also harder to pull a vacuum going this way.

Does it make sense that this valve goes between the vacuum advance on the distributor and "tees" into the right-hand intake maniford and vacuum advance dump valve...with the DIST side attached to the vacuum advance?

Thanks!

John
1987 XJ-S V12, 62,000 miles

 

Make sense? HA! The vacuum advance system is complex. I could barely make sense of it when I actually owned an XJS. Years later, even less :-)

The factory shop manuals/ROM and parts catalog have some good descriptions and illustrations of how it all works. Kirby's book likely has good info as well. Also take a peek at the AJ6 Engineering webpage.....there is (or at least used to be) a section on older V12 fuel/emissions/ignition systems.

Sorry I can't be of more help. Others wil chime in.

Cheers
DD

 

No worries Doug, thanks for the response. It'll get sorted out soon enough. For now, I've got bigger issues (see new post)...

Thanks,

John

 

Best idea is to scrap the entire lot of the vac tube stuff and run a single vac tube directly to the vac capsule from the B bank throttle body, there is a suitable port on the underside.

Also, junk the 15 minute timer which means the engine runs too rich for 15 minutes. To do this, just pull the wires off the thermostatic switch on the A bank cabin end water manifold. Pic available if you need it.

Then as you have removed the CC, you can take off all the unused junk (vac switches, little blue boxes, etc etc) associated with the vac system. Also remove an entire bit of loom which goes to all these things down the A bank topside of the engine.

I did all this about 10 years ago, and it is great, and no problems of any sort, cold or hot.

Greg

 

I realise I’m digging up ghost thread well from the past here, but I really want a little a little information on this.
Greg could you post a couple of pics or diagram on what bits to dispose off and which tube goes where, I like the simplicity and work very much on the "KISS" factor, its something I want to do to mine mine before I convert to Distributor-less igintion, on the cards but when not sure.

 

Katoh
Before replying in detail about the vac pipes a few questions:
Is yours a Lucas or a Marelli car?
Have you removed/do you want to remove the CC?

As far as the the 15 minute enrichment timer switch in concerned: On the A bank rear water manifold, look for where the heater water inlet flexible pipe pipe takes off from the A bank water manifold on its way to the heater valve on the firewall. Right next to the water take off is a thermostatic switch with two connectors. The rear water manifold is under the inlet manifold and above the heat shield at the cabin end of the engine (basically at the opposite end of the engine to the thermostat housing). Just unplugging the two connectors and insulating them separately and tying them out of the way somewhere disables the system.

Greg

 

Thanks Greg
Lucas
I take it CC is cruise controll? Its still in place and I wish to keep it, If I have to remove it to get at parts no problem whatsoever.

The 15minute timer I deactivated first day I bought the car, read through Palm's book and that was the first to go, just did exactly what you described with disconnecting the two wires.

 

Katoh

On the Lucas cars, as you know, there is a hideously complex set of vac pipes and little actuators and switches and units of various sorts to modify the vacuum seen by the advance capsule signal on the dizzy.

All this can be removed, 100%, and be replaced by one vac tube running from the little spigot you will find underneath the A bank throttle butterfly body direct to the vac capsule spigot.

All miles simpler and you will not notice any difference.

I have a vague feeling, and I am sorry I cannot be more specific, that this system may interface with the CC vac actuation system at one point, so some care might be needed to ensure the CC system does not leak vac. On my car, the mod did not affect the CC, before I removed that too. Take a look and see, it may not. I think the Great Palm might mention it too. In any event, your revered countryman G Francis will certainly be able to advise.

Greg

 

Do I ever, Reminds me of an old Monty Python scetch, Where we need to have a meeting to discuss when to have our next meeting in regards to our last meeting about the meeting before! Just a bunch of useless bits that had to be there to justify their own importance. Wow I just summed up upper management in 99% of Everthing!

I will have to just tract things back from the dizzy, and chase the individual lines to see if there is some sort of interface with the CC, No doubt I will be pestering you again on the subject, to make things simple and anyone else following this I will simply continue on with this same thread. In the meantime I might look through Palm's book again and refresh my memory.
Thanks for all your Advice!

 

Will deactivating the 15minute timer have a positive impact on my gas mileage...?

 

Simply YES!

In Palms book around page 130-140 in there is a good explanation of what the timer is and what it does.

 

So where does one get the K. Palms book?

 

Here you go, its a free download, no XJS owner should be without it.
Kirby Palm's Jaguar XJ-S Help Book