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The sensor in the diff is unlikely to have failed. More likely is the interface unit in the trunk (boot). Paul (PTJS1) on here can explain what to test first, as can others.
Last edited by Greg in France; Sep 12, 2022 at 04:23 AM.
Any advice on what to test to get the speedo working again would be helpful.
Reverse lights not working also needs to be delved into.
Part of the "joy" in getting a new car is sorting out the things that need sorting as well as overdue preventive maintenance.
In addition to plugs and the Magnecore wires, and "while in there", I ordered new cam cover gaskets, the solid aluminum half moons and new intake manifold gaskets. Seems logical to do everything at once while it is apart and have the easiest access. And I believe I can see that the cam cover gaskets are leaking at the rear, probably around the now hardened original rubber half moons.
New NGK plugs, cap, cap gasket, rotor, Magnecore wires and two new NGK coils. I went with NGK BR6EF plugs per Jag's service bulletin gapped to .025. Contemplating doing the distributor shaft and silicone in the rotor mod.
The plugs looked a little darker than I would like, but maybe the hotter ones will do better.
Last edited by MSGGrunt; Sep 16, 2022 at 07:11 PM.
Injectors are on their way back from Injector Repair LLC after being cleaned and tested. This is the write up from Jim.
Your set of twelve Bosch injectors flow tested good right out of the box (after an initial exterior cleaning / de-greasing), and flow tested at close to a 6.7 % flow balance (42 to 45 cc). A 6.7 % flow balance is 'okay' for a used set of injectors but should be a little better. The spray patterns were all good. All of the injectors held pressure (no leaks).
The engine should have run okay with these injectors, maybe a tiny bit rough. They were perfect thru all the different flow tests performed. An Injector Flow Balance of under 5% is considered necessary for proper engine performance. When I sell refurbished sets, I try to get them flow matched at one to three percent flow balance. The closer the flow rates of the injectors are to each other, the better the engine will run, the engine will run smoother, and get better
miles per gallon.
This microfilters were in good shape. When I backflushed the injectors, no visible debris came out of the injectors. Inside the injectors was clean (nice). The discharge tips were mostly clean.
Attached are pictures of some of the multiple flow tests I ran on your set of injectors.
Pictures # 2783, 84 are of the initial dynamic flow test (before cleaning).
Pictures # 2785, 86 are of one of the final dynamic flow tests. I ran all tests multiple times.
Your injectors final flow tests were much better. The final dynamic flow test (12 ms pulse width / 2400 rpm / 25 seconds) had flow rates of 45 to 46 cc.s across the board. The Final injector flow balance improved to close to 2.2 %. Good to go.
They all performed flawless in all the tests.
The injectors held pressures over 80 psi without leaking a drop, and their spray patterns were perfect.
<I would paint the grill black to give it some contrast>
I would never do that, it's one of the points that identify it as a V12, like the body color headlight surrounds and the mirrors.
Once you do that next thing you might try is telling your girlfriend to change hairstyles.
Last edited by equiprx; Oct 1, 2022 at 04:36 PM.
Reason: another thought
Just finished replacing the cam covers and by default the intake manifold gaskets. After the computer relearned everything, the car seems to like the new NGK plugs, Magnecore wires and Marelli cap and rotor. I replaced the rubber hoses that were cracked and or dried out.
All back together, but still may need some final tuning by someone who knows these V12 engine better than me. It is my first and only about 100 miles into ownership.
When I got the car, I quickly discovered that the backup lights were not working. I ordered a new back up switch, which turned out to be the wrong one, but ended up not needing a new switch after all. The switch "cam" would turn on the lights if I pushed back on it by hand, but it must have gotten lazy over the years and the shifter lever didn't push it back far enough to illuminate the lights. A little tweaking (bending) of this arm has the lights working one again.
Paul has inadvertently posted his reply on another thread, I am pretty sure. This is what he posted:
Is the trip computer registering distance and speed? If it is start by looking at the circuit board on the instrument cluster and particularly the earth. If the trip computer isn't working check the integrity of the wiring on the diff sensor and the wiring plug connection above it in the car.
Paul
__________________
79 XJ-S Pre-HE
94 XJS 4.0 AJ16 Conv
06 4.2 S/C Jaguar Engine (but not in a Jaguar body...)
I just recently purchased the vehicle, but I do not think the trip computer is registering anything other than the time and it did display a fault code. I know the odometer and trip meter under the tach is not registering anything.. If it matters, the tach and all other gauges working properly.
I assume easy enough to unplug the connector at the differential and clean it. Same with the plug inside the car.
Last edited by MSGGrunt; Oct 11, 2022 at 06:54 AM.
If you don't have any readings on the trip computer, then first check that you're getting a signal out from the speed interface unit in the boot. If you're not seeing something there, then start working back to the sensor unit wiring.
Others have talked about the need to remove the plug inside the car when dropping the rear cage, but I can definitely get the sensor out of the back of the diff. Just be careful when pulling the sensor out as it is easy to damage the nose of the sensor on the diff casing. It's also really critical on the air gap, so make sure you don't lose the very thin spacer gaskets.
I know it's probably covered in another thread, but do I just lift both rear wheels off the ground, put it in drive and see if there is a signal coming out of the diff sensor?
The car, being new to me, is still being sorted out a bit. I have had a "hunting/surging" idle issue and recently replaced the auxiliary air valve and now all is well.
The warm RPM in park is still a bit high at 1000 rpm, but I am hoping this will be resolved by having the motor tuned by someone who know these V12s intimately. Donovan Motor Car Service is pretty close to me and I have heard great things about them.
If the tickover is too high screw in that huge bolt on the AAV to bring it down. If that bolt is all the way in, then you have q small air leak. In which case the first thing to do is to set then butterfliees to a 2 thou gap and then adjust the AAV bolt out or in as required.
The bolt is screwed in, I believe, about as far as I can screw it in, the throttle plates have been set and the engine smoke tested. No leaks other than out through the throttle plates.
