FWIW....

IMHO this (and most others used XJSs out there, really) would be a prime candidate for "cleaning the vee". Remove everything in the Vee, clean it, repair/replace all wires and vacuum hoses, new fuel hoses, new FI harness, new plugs-plug wires-dist cap-rotor, repair distrubutor vacuum advance and mechanical advance, reseal cruise control bellows, new intake and cam cover gaskets, clean throttle bodies, new throttle businhgs, synchronize throttle linakges, etc. Get it all in one big shot.

Cheers
DD

 

i agree.

 

can anyone tell me which way the 1a cylinder on the distributor is pointed? mine is pointed almost towards the 2b spark plug, which judging from some firing sequence diagrams would suggest that the timing has been retarded drastically.

 

That's not too far off.
You can adjust the timing with the cam-screw on the side, but if you take the cap, rotor, dustcap off you will see 3 allen screws that hold the dist in place and there is some adjustment there as well.
Before you mess too much with it, do yourself a favor and fix the wires first! I thought my timing was messed up and screwed with it for quite a while before I found it was in the wiring!

 

If you have an XJS, this is the book to have, should give you a lot of help with your car.
Hope you like reading, it is 700 pages, and is an incredible project to help Jaguar owners.
Free download
Kirby Palm's Jaguar XJ-S Help Book
good luck
Pete

 

I sent the injectors and one spare connector with wires, from BMW.
All fuel pumps are gone, apparently my eBay dep't sold them all off...Sorry, will refund $10.

 

dont worry about it bro. $20 for 2 injectors is cheap in my book.

 

If you look carefully, there should be a tiny "1" cast into the distributor cap, about in the direction of plug 2B/3B. This is the place for the arm to be when the firing time comes for plug 1A. I 100% agree fix all the wiring etc, before doing anything to the timing. It is not that easy to change the timing significantly without (as someone already mentioned) delving into the dizzy and undoing the three securing screws.

On the other hand, it is very easy to get a plug wire wrong, or forget they go anti-clockwise!

Greg

 

already checked the plug wires. theyre all good.

 

Welp, thanks to Mish ive got the new injector in for 2a and the Jag is officially running on all 12. its idling a little bit smoother and runs about 8.3% stronger.

its still running REALLY rich and it cuts out if you give it too much throttle. its much worse if you reconnect the Vacuum ECU hose. so no improvement outside of the small performance increase the 12th cylinder makes.

 

This really sounds just like the symptoms I had with mine. No matter what I did I could not get it to run any leaner. Once I replaced the brittle wires it was like a totally different car. Considering how the wires to the ATS and CTS in your picture look like they've been messed with, I'd suggest starting with those and replace them back to where they come out of the fender.

 

did yours start running better after harnesses or after a total engine bay wiring job?

 

Oh yeah!

 

not sure what you mean

 

Sorry, I replaced the injector harness long before I even got it running. There was no doubt it was bad, I could see bare wires.
The car didn't run good until I'd replaced the rest of the wires though.

 

****.
any idea, specifically, what wires caused your car to run like that?

 

The CTS, ATS and TPS are all connected and go into the ECU, and I think the breaks in the wires were causing weird readings in the ECU.

 

Another thing you should really need to check is the TPS under the throttle "capstain". They're known to go bad and if yours is telling the ECU that the throttle is wide open at idle, it could be running rich for that reason!

Check TPS voltage at the square 3-wire connector where it come out from under the capstain. Unplug it just a tiny bit so you can see the metal connectors and with the key on, engine NOT running, probe the red and yellow wires. It should read about .32-.35v at idle position and 4.8-5.0v at full throttle position. Voltage should increase smoothly as you open throttle.

I'd like to take credit for all this info, but honestly it's all gleaned from Grant and Doug!

 

the original owner told me the TPS was the only thing he hadnt replaced. not only had he not replaced it but he removed it from the throttle capstain and laid it aside. it does have a small effect on the idle when opened or closed and when i put it back on the throttle capstain it didnt seem to run any better. its also missing a wire that should be going to the middle pin.
also i have to let off the throttle for the transmission to upshift. if this was on either of my Grand Prixs there would be no doubt in my mind that it was a TPS issue. however, i have no idea if the V12 TPS controls shift points.

 

i think im thinking of a different switch. your talking about a potentiometer type thing right? and im talking about a trigger switch that the throttle linkage flips on at about half throttle. it has no intermediate setting.