Over the last few days I realised my 85 V12 XJS HE was running very badly and sometimes pinging.

Did some investigation today and found the distributor was very loose. Removed the cap and found the 2 allen scews were undone, no problem tightend them and went to adjust the ignition timing back to 10 degree BTDC. As much as I fiddled the best I can get is 20 ATDC. I have moved the distributor as much on the allen bolts but I still cannot get the ignition timing correct, what has gone wrong?

How do I move the ditributor round some more as the vacuum canistor is now catching on the coil? Am I missing something here?

Steve P

 

I'm not a jag expert, but my first guess would be your distributor jumped a tooth when it was loose, you can adjust for it a little, but not enough to make up for one whole tooth.
If it did, I'd make sure to inspect the distributor gear to make sure that when this happened, it didn't bugger up the end of the gear!

 

There's another adjustment.....a cam-like screw at about the 2:00 o'clock position if you are looking at the distributor from the right fender. Try that....you might get more adjustment.

Not sure where 10º BTDC came from.....the correct setting is 18ºBTDC at 3000 rpm with the vac advance disconnected

Cheers
DD

 

OK the mystery is getting worse.

After much fiddling I discovered the timing was running at 5 ATDC at 3000rpm with no vacuum, I tried to adjust it but it looked like it had jumped a tooth or something similar.

I removed the distributor and tried to set it up as per the manual, even though it is now nearer 15BTDC at 3000rpm it sounds like is pinging as soon as you touch the throttle, it is also very slow to rev.

Can the timing mark be wrong on the front pulley? Is there any way of checking TDC is TDC?

What could have caused the distributor to go loose in the first place?

Not sure if what to try next?

HELP!!!!

Steve P

 

I hate to say this but now I'm thinking timing chain. I'm interested to see what replies you get and what the final outcome is!

 

Yes, the balancers can delaminate....which would bollix up the timing marks.

Cheers
DD

 

Took the day off work yesterday to try and get her runnuing again.

First of all I used the timing marks to set the distributor, it started just but ran with lots of backfires.

Secondly I took no 1 spark plug out and using a piece of rod found what appeared to be TDC. Marked this on the bottom pulley and it was 45 degrees away from the original mark. Used this to set the distributor and ran but very lethargick.

Thirdly I did half between the 2 marks out of desperation and it would not even start.

Gave up then as the battery was flat.

Anybody got an idea of how I can get an accurate TDC?

If I did find it and it did not run what else can it be?

Low fuel warning light came on yesterday and I am not sure to put it in or over it.

Help!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!11

 

Honestly if you can find a whistle that goes in the spark plug hole and will whistle when the #1 piston comes up on TDC. Or your rod will do but you need to see the intake valve open then close.......as the piston comes then you are on TDC however I belive (and I have never had the timing chain apart on a v12 ) but I feel like you are going to have to expose all of your timing chain and gears. That has jumped and I don't believe it was in the DIST. I feel like the problem is in your chain jumping a tooth or three.



Brian Felts