So heres some quick background since this is my first post.

I am very mechanically inclined and both restore classic vehicles and build new school cars.

This is my first dip in the Jaguar pool however. I purchased this 76 xj12 from a guy who purchased it from someone who purchased it from someone etc, always in non-running condition. 89xxx miles on a surprisingly mostly untouched car. Has not ran in 22+ years.

I brought it in the garage and started prepping it to try and make it fire going through some quick checks, new gas, getting the fuel pump working again, etc. The car actually fired right up! But ran quite horribly (quickly finding out the distributor was seized almost everywhere possible). So i tore into it and completely cleaned and refreshed it. The four nylon screws holding the trigger board obviously snapped and are temporarily replaced with stainless screws. Newer cap, original rotor, pickup module, ballast resistor, trigger wheel, etc. Newer plug wires. The ignition amplifier was previously moved to the radiator support area.

I reinstalled the distributor on the 1A Compression Stroke @ 10° BTDC and centered the vernier gauge on the distributor. Rotor was pointing to 1A on the cap (drivers headlight). Now the car wants to fire right up but shuts down right after it gets going to where you would return the key to run position. Getting plenty of gas. After a few cranks itll end up dripping from the throttle bodies. Getting a nice blue strong spark from the coil. The ballast resistor block showed 12v in and out of each connection and ohmed out similar to the xjshelp.pdf i have spec'd however the bottom two resistor tests were slightly off spec. The .72-.80 spec ohmed out around 1.5 and the last spec was about that far off as well. Are these values correct? Whats causing this issue? Trigger board to rotor clearance? The rotor did fall a few feet to the ground at one point in the garage and landed on the copper rib tip but did not seem to damage it. Ive tried setting the distributor at various inital timing positions with no success.

One thought i had... my pickup module harness coming from the distributor... has four wires coming from it. Three go into the connector (similar to trailer wiring harness addons) and one wire came from elsewhere. Wire was just laying there with exposed strands. I put an eyelet connector on it and wired it to ground. Is this correct?

Also, with the newer ignition amplifier installed, the previous owner rerouted the tach wire from the car bypassed the ballast pack and has some inlike 7.6?k resistor inline and then is connected to two wires one of which goes to the amplifier and the other to coil neg i believe.

What am i missing here??? I've been reading every book i can, futzing with a few things everyday nonstop to no avail. Sorry about the long read, just wanted to be as descriptive as possible.

 

Hang in there. Grant will come along soon. Of the regulars who post here he's the one who knows/remembers the old 'Opus" system best.

I could offer a couple very speculative tidbits with the proviso that Grant double check what I've said.....so best to just wait for him to come along.

Cheers
DD

 

I'm back.

Had a Valentines offer I simply could not refuse.

You have done well, CONGRATULATIONS.

Your problem is SIMPLE, like ALL V12's.

The 4th wire is a 12V Ign feed for the hall effect sensors in that trigger board.

Remove it from the earth, connect it to a GOOD 12v IGN ON feed. NOT the coil, or the ballast.

I use one of the relays close by.

Since you dropped the rotor, too much JD I suggest, test the heel magnet for magnetism, as dropping a magnet does reduce the magnetism significantly.

 

There's my savior! Haha. I found it weird i didn't really see that fourth wire in schematics, unless i kept overlooking it.

As far as the magnetism of the rotor... what would be my best way of testing the strength of polarity?

And are the nylon screws that hold the board important? Or even available anywhere? Cant wait to get back to the shop now that i have some basis to work with. Thanks in Advance, hopefully this cures my issue

 

OK, here goes,

That 4th wire will NOT appear in any schematics. The original was a 3 wire board with "reed switches" imbedded in the mastic gunk. RELIABLE?, no. Hence the quantum leap to hall effect sensors and the 12v feed to activate things.

Testing the strength of the magnet is as basic as using a steel something, and ensure it basically "sticks" to the magnet with some strength. The original magnet was never very strong, so dont expect real lifting strength, just a basic magnetism will activate those switches.

The nylon screws are preferred, along with the grommets at each corner of the board. One of mine had missing screws and grommets. I located 4 grommets and that gave me the required spacing for height of the board, and used some stainless fine thread screws to secure the thing. That was 16 years ago, and still as was. Never saw a need to return and do any more with that one.

I had a part # for those bits, and when and if I find it I will update this post.

 

Went looking.

Found the parts packets with 1 screw in it, and 1 grommet.

The part # for the grommet is DAC2741.
The part # for the screws is ???????, label is gone, sorry.

I know, I'm a hoarder.

Try SNG Barratt, or XK's Unlimited (San Louis Obispo). They have helped me over the years with odd stuff.

Once one of them keys in the grommet number, the screw number "should" connect. That would depend on how switched on their software, and operator are haha.

 

It's been some time since I've tinkered with the pre-HE D-Jet efi. It seems to me that the 76 is starting on the cold start injectors but the mains aren't operating. Hence, the quick shutdown. Getting the Hall effect trigger working should bring them online and you should have a runner.

 

This weekend i went out to the shop and went ahead and wired it up to a 12V ignition feed and sure enough, fired right up! Cant thank you guys enough. Now, time to dig way into this thing and bring this sleeping cat back to life. The throttle cam is a bit tight as are the butterflies (and everything else haha). But of all the years ive been on forum boards its nice to know that i can count on real expert feedback here. Ill post up a thread or two on the restoration progress of this xj throughout this spring/summer.

 

I am really impressed with your skills. I am serious. Grant/Doug and others have had to hold my little hand through the work I have done on the 77 XJ12 I have been slowly tinkering with.

Here is what I have learned regarding a cream puff that has sat for 20 years as well. Mostly simple age related stuff.

1. EGR valves opened whenever the hell they wanted to. I just sealed them both off with a SS plate at the four hole mounting flange.

2. Both fuel level units in tanks are shot. One gone (but reads 3/4 full) and one an eight tank off.

3. Fuel return lines in trunk were leaking and bleeding off residual pressure in about three seconds. If no residual pressure (or holding pressure while you start), no robust kick from the CSV's.

4. Trans mount rubber buffer bushing was shot. Could have skipped that one as it's not that critical but trans was leaking and......while you are in there replacing the pan gasket and filter......

5 Top shock bushings - inner fender side - were pancaked and crumbling - noisy over any bumps.

6. AC system held vacuum but out of R-12 (big news, right?)

7. Seal on steering rack tower is flowing the red stuff freely.

8. Three of four ball joint boots are gone.

9. Tires, believe it or not, the original Dunlop Elite 70's were, um......not round in the slightest.

10. Passenger bank fuel regulator was shot - I actually brought it back to life with PB blaster and some soak time and - but for $75 including shipping I bought the same Bosch part that was on it.

11. Headliner is sagging.