I think the Devil or Mr. Murphy or both live in this car. This all started Friday the 13th!

First the fuel pump died, then the fuel pressure regulator and the alternator quit charging.

Now, when allowed to get fully warm, either by driving in traffic or idling
in the driveway - the cars idle bounces from 600-800 and it runs poorly (again). Will check the fuel pressure when it cools down as it would not
restart and the fuel pump just kept "working".. not sure if it is pumping
fuel or just trying to pump. Will confirm there is fuel moving and the filters have not gotten clogged somehow.. they are near new.

Plus, the instrument gauge lights, tach light and speedo lights are not working... along with the Map and lights under the parcel tray.

The relevant electrical checking results are below:


No power at RW wire on gauge panel multi plug

Power on Purple wire on gauge panel multi plug
Map Interior switch has no power to it in either position.
Inline fuses in the gauge panel are good.. but no power to them or out of them

Fuses 1-4 good with key on
Second set of fuses good with engine running and headlights on.
Purple wire on the multi plug in the back of the gauges has battery voltage

All other features work.. radio, heater fans, AC, outside lights and turn signals etc.

No power on any RW wire in the dash and that includes RW wire that feeds Red wire to light in parcel tray.. but if I jump the connection of the two parcel tray lights wires with 12V..All the Instrument lights and the clock and gauge lights will work but they will then stay on.

Again, nothing done to electrical system except getting the alternator working by the removal of the un-needed wire on Pin "S" that had been
there for many years. Alternator is still charging perfectly.

 

Wow, and all I did was disconnect a wire that had been there since 2008!

 

My buddy and I have studied the electrical schematics and have some ideas
on where to look for the problem.


Will get to it later on today and report the solution - this time.. then
I will park it in front of a Catholic church for a period of time.

 

Roger:


It must be endemic! I've been fighting electrics since before Christmas. It "started" with an occasional failure to crank. Just a clunk on twisting the key. But, then a whack or a twist and it would crank and run just fine.


I "started" by rebuilding the starter relay with a new unit and connector in lieu of separate spade connectors. Purple and pink wires (GM)_ bedeviled me as well as the neutral start ground.


Then I found a non responsive "starter". Got a new Malasyian unit. good crank, but odd reponses on the key position vs dash lights!!


Then uff" it quit in a cloud of smoke on the road nearby. Flat bed home. wow, burnt starter cable at the solenoid. Got a new generic one. Much stouter than the jag version.


New to me entire ignition switch from David Boger. Major thrashes to get the old out and the new in.


Now, good crank, may or may not "start"!!


Yesterday, checked battery with Schumacher smart charger. OH, oh, 50% and just over 12v ! Starter hogging the volts with little left for ignition and injectors or pump?


Charged most of yesterday. Now 100 % and 13+ volts. More thrash later????


I have a codicil for Murphy's law. "..... and once having gone wrong, will remain so indefinitely..."


Electrickery at it's best/worst.


Carl

 

man I haven't had those kinds of problems, never in my '84, talk about reliable, but then I don't mess much with the electronics. Same with my S type, never an electric problem.

remember I bought my XJ-6 in 1989, still has the same old starter though it sometimes screeches like a screeching witch, but it's only like once in a Full Moon, usually near Halloween.

 

By testing all the pins on the headlight/side lights switch.. they were fine and the fuse has power when the switch is on.

But, I compared the wiring on the '72 to my '71 and noticed some differences.

The RM wire from the loom was connected to the Red wire that goes to lights below the parcel tray. But, on my '71 that Red wire was on the
bottom LH fuse - there was a open connection. When it was on there I went on to the Red wire that was now hanging loose.

There was supposed to be power on the RW wire, I made a Red jumper wire and attached it to front left pin (not sure of the number = 3?) and
now the lights all worked.

Just the clock left to make work... the power wire going to the clock was "hot" but the little nut holding it down was not tight.. tightened it
up and all is well on the dash now.

Went for a long freeway test drive of 20 miles, filled up the two tanks with the needed 91 octane for the LT1 and drove home. One block from
my house it stalled at a stop sign. No scanner codes and the SES light was on so there was power from the PCM. It started right up and I drove
to the driveway where it stalled again - coasted into the drive. It started right back up again..

When revved high and held it had a miss and the 02 sensor readings were wild, especially the right one that dropped to 4 mv and then went wildly
back up to 836 mv... will check for vacuum and exhaust leaks but I do not hear any exhaust leaks?

Some major progress was made today... but more discovery yet to be done. In defense of the Jag, the PO had already done/had done the conversion when
I bought it. It barely ran enough to drive home - alternator not charging due to bad feed wire and the injectors were badly clogged and the tank wiring
and plumbing was incorrect. Plus all the other things that needed fixing.. This car has not been driven 150 miles in the past two years while it was getting
a total down to bare metal repainting with all new rubber seals and new S3 seats and matching upholstery and many other modern mods.