Any words of wisdom on tackling wiring?

(David Bandel) #1

I’m lumping an '83 VDP with an '01 Ls1, kit from Jaguar Specialties, and it’s been slow going with my schedule. I’ve done a few Jeeps prior, but for some reason I’m dreading this part of the project, particularly the stock Jaguar FI wiring hanging out of the firewall. Does most of that just get ripped out? Looking at the schematics It seems like I’ll only need the connections from the ignition switch, fuel pump relay and tachometer. Any words of wisdom or experience appreciated as I try to stay motivated.


(Carl Hutchins, Jr. ) #2

Well, it has been decades ago, that I tackled the mating of the electrics in my LT1 swap.

I cut all the wires in the cabin that ran along the center tunnel. Ugh, too much. I needed the fuel pump wire. Not the worst of things. I merely spliced in a lead to go back through that grommet under the battery tray.

In the engine bay was another matter.

  1. The “right” place to connect the Jaguar Speedo. I chose the wrong one!!!

  2. Where to find a signal for the tach. At the PCM or the coil. I chose the coil.

  3. Used Andrew’s plan brake switch to iinterrupt the Torque converter lock up.

  4. Used an XJS shift tower sourced from Andrew. Better detent match and a better provision for starter inhibit.

  5. Tapped in my after market E fans to the GM relays for fan 1 and fan 2. An all weather trailer connector worked nicely.


(Doug Dwyer) #3

I’m thinking the big fuel injection harness can go.

Tach, oil pressure light and gauge, alternator warning light light, a/c compressor wires are in a harness down low on the RH wall of the engine bay with a connector joining the engine half to the cabin half.

Leave as much wiring to the firewall relays intact as possible until you finalize your wiring scheme. You might need it for the fuel pump and starter, and it should have some “12v with key on” wires (solid white) that you’ll probably need.

Others will chime in



I just ordered the jag specialties kit to do put an ls1 in my 71 xj6, but have not received it. I recall Andrew mentioned a wiring harness they make for your year, that I didn’t need due to the simpler factory wiring. isn’t everything covered in the conversion manual?

(David Bandel) #5


I have Andrew’s adapter. I’m not worried about getting the LS1 running, what I’m trying to figure out is how much of the original wiring I can remove (to clean things up in the engine bay and trunk). I probably need to go through the entire harness wire by wire, but being lazy I thought I would ask here first. ;^) I’d like to remove the original Jaguar Fuel Injection ECM from the trunk but I’m not sure if that will mean rewiring something else later.

(Doug Dwyer) #6

When I did my 6 cylinder-to-V12 swap I had the entire F.I. harness out of the car (about 15 feet long!)

The F.I. harness is virtually a stand-alone thing. As I recall the only part of the harness that ties-in to the rest of the car is one wire feeding the ‘interface module’ for the trip computer.


(Carl Hutchins, Jr. ) #7

I let most o the long Jaguar EFI harness in place.

The ECM went on to help a guy in Texas after merely al9ng for the ride for a time.

Not sure if the trip computer wire is there. If so, it got cut!!! but, the unit spits out odd data!!! The clock works OK!!!

I found white wire, hot only in start and run, at the low coolant capsule at the ight “B” post.

I created two racks to replace the Jaguar relay rack. Only the horn relay is not attached there.
And, alongside, a ground bus. All relay ground legs, except the starter relay, and of course the horn relay ground there, and in turn at the wing wall battery ground.

Op and coolant sensors are Jaguar units and adapted to the GM block.

Among my unexplained mysteries is the need for a diodes on each leg of the load circuit of the starter relay?? A need for a back feed preventer.

The Johns cars instructions tell how to do it, I too new at circuitry at the time, did not get it, The electric whiz there made a simple connector one for me to include them.



(Roger Mabry) #8

Wait until you get Andrew’s kit…he does excellent job on the wiring. Or, just contact him with your questions…

(Robert Stephens) #9

Completed a LS1 conversion 18months ago.
All I did was cut the FI harness at the fire wirewall, left the cables inside the car, then cut the wires from the boot (trunk).

Had a guy here in Australia modify the wiring loom from the LS1 and removed all the unnecessary wires from the loom, added a fuse & relay box and all I had to do was connect up 11 wires for the following.

  1. Brake switch
  2. Econ / power for TX
  3. Reversing lights - I didn’t use as used the existing jag one
  4. Ign supply
  5. Start signal from ign
  6. Alt / bat light
  7. Speed sensor (used Jag Specialities unit) to convert signal to 85XJ elect speedo
  8. Tacho
  9. Oil
  10. Temperature gauge
  11. Air Con

Then had to connect a power supply to relay box which came with a relay for ECU, fuel pump, 2 thermos fans and starter. This allowed me to remove all the old jag relays under the bonnet.

If you don’t like playing with electrics may I suggest you use Jag Specialities as they can supply a suitable harness.

regards Rob.

(Bob Loftus) #10

I suggest you track down a copy of Jaguar manual S57 wiring diagrams for the XJ6 Series III. It was a necessity when I installed a 96 LT1/4L60E FI engine/trans into my 83 XJ6. Ignoring the Jag FI harness which was an add on and separate, the basic Series III wiring is pretty simple as long as you have the decoder ring (S57 manual). I concur with the others. You can cut/eliminate the original Jag FI harness with the exception of the wires to feed power to the fuel pump and the trip computer if you desire to keeping it active (another topic in itself). Does your donor engine include it’s original PCM wiring harness? Does it include a relay/fuse box? Are you using an aftermarket harness?

(Carl Hutchins, Jr. ) #11

Ditto :slight_smile:
Bob shared his S57 with me. Plastic jacket for each page. Invaluable. The easiest schematic to read that I’ve ever seen. A tutorial in itself.


(David Bandel) #12

Thanks for the replies. Hard staying motivated when it’s below freezing and the heater isn’t keeping up in the shop, and trying to trace wires with gloves on. ;^) I’m using Andrew’s kit so not too concerned about getting the LS1 to fire up but I want to clean up the engine bay as much as possible (without cutting anything I’ll need later, (thanks for the warning Cadjag1!).

Now I just have to find time. Just finished replacing the engine in son’s Jetta, now I’ve been helping him rebuild twin SU’s for his MGB to replace a crappy Weber mod. Then need to do some maintenance on my truck and the XKR. It never ends…