I recently acquired a MINT condition 1990 XJS V12 in Jaguar Racing Green with a Barley interior. It now has 116,000 on the clock (115,750 when I bought it). I have all service records, all original brochures, window sticker, etc. All the goodies.

I work in a Land Rover dealership and never thought I'd be a Jag owner but this thing was so cherry and sat in our showroom since November. I had to get it. I used to be a technician here and am pretty familiar with Lucas systems and being ASE I figured hey I'm just crazy enough to own and work on this thing. I bought it as a Sunday driver so I only expect to drive it around 2,000 a year.

Had a hard time starting and running after it sat in the showroom for a couple months and it had a small leak. I'm familiar with the jokes on older jags/landys about leaking oil and I wasn't affraid to deal with the challenge. The fuel smelled varnished so I figured from looking at the records it really didn't need anything except for a battery, fuel stabilizer, and tune up.

Did the battery, tightened a ground right next to it, put stabilizer in and ran a bunch of fuel through it and vuala. Ran as smooth as I'd imagine except for a light mis that I figure the tune-up will take care of.

Yesterday I started the tune up(distributor cap, rotor, wires, plugs). I did it according to "accessing the vee" except for taking the entire TB tower out I just removed the top. I have thin hands and good in small spaces so I'm not worried about the two plugs on either side.

Now I come to the whole reason of why I'm typing this. What is this diaphragm/breather/pcv deal with two wires sticking out of it on the backside of the v. The rubber itself is cracked and by the looks of it, the oil leak is coming from under it.

I tried typing those into google and couldn't really find much on it but I did find this forum and I'm hoping you guys can shed some light on this.

Also, um I couldn't really get the distributor out with the wires attached so I pulled 'em and uh yea... I took a lot of pictures before hand but if someone knows where I could find a diagram for the wires, that would be great.

Any and all help is appreciated

 

Nevermind. I checked when I got home. What I thought was a diaphragm is just a dust cover for the connector of the oil pressure sender & light switch and the junction they're both on. I noticed the lines going to the heads were seeping when it was at the dealership. Now I'm pretty much just talking to myself.

 

Lol, well welcome to the forum anyway! You had me scratching my head trying to figure out what diaphram you were talking about! Those sending units are notorious for leaking, think of them as an early warning device, if they stop leaking you're out of oil!

 

Well put James! And by the way, hello again! Haven't talked to you in over a year. Hope all is well.
I resealed the whole top end on my 85 HE, and still deal with some annoying little seeps from time to time.
There is an old adage that goes "you can write the names Harley Davidson, Detroit Diesel, or Waukesha on a piece of paper and put it in your pocket; guaranteed your pocket will leak oil!" Guess we could write Jaguar on that list too eh? Hahaha!!

 

As far as your distributor plug wires go, the V12 is basically two intertwined six cylinder firing orders. 153624 on each bank. I don't remember which is a bank, but I believe it's the RH side. So the firing order (which btw is also on a decal on one of your air cleaner covers), is 1a 6b 5a 2b 3a 4b 6a 1b 2a 5b 4a 3b. I think... Been awhile. Your cap should be labeled for #1, and by rotating the engine with the cap off you can find the rotation direction of the rotor.
Hope this helps.

 

replace the idiot light and pressure sender at the same time sense they will both end up leaking and you are already down in there.

You may want a crows foot for removing the sender.

I inspected my vacuum and mechanical advance (for the first time) a few weeks ago. The only thing you need to remove for the dizzy and wires is the cruise control. The plugs though...yea, maybe need to move the tower for that, can't remember.

To get to the sending unit and idiot light you will need to remove the vacuum lines at the far back of the v.


The wiring diagram should be on the hood or on the air cleaner housing.

 

Thanks for that. Btw I'm located in Albuquerque.

 

If you have Lucas ignition, there should be a tiny "1" moulded into the top of the distributor cap, just behind one of the spark plug HT push-in terminals. Looking down from the top the "1" will be pointing roughly towards the B bank number 2 plug. (ie USA driver's side bank of the V second plug from the front).

In this "1" terminal on the distributor cap goes the HT lead for the A bank number 1 plug - that is the frontmost plug on the USA passenger side bank of the V.

After that, the firing order goes anti-clockwise looking down from the top.

Greg