1992 Facelift 5.3 Engine Wiring Harness Rebuild

Slowed down a little bit. It’s a little cold out and no heat in the garage. I’m from the midwest but I have acclimated to Pacific Northwest temperatures. Apparently anything below 50 degrees F is cold.

Also, I have been doing quite a bit of cleaning along the way.

I did get to some shielded wire last weekend, but not the power modules I had hoped. Just the TDC Sensor.

Started on the coil/power module wiring. The diagrams threw me off a bit. It looks like another typo to me, but maybe I’m missing something. Fig. 26 shows 8 white wires connected together:

Fig. 27 shows only 7.

I’m fairly certain the 7 is correct and is actually 7 wires connected at one splice.

I need to splice the shielded wires from the engine to the harness in the cabin. What’s better:

  1. Using a crimped connection, insulated, on the conductor(s) and soldering the shielding around that connection

  2. Using a jumper from the shielding to a connector and the re-jumpering from the other side of the connector to the shielding on other side.

I would go for option no.1

I was kind of under the assumption that some of the wiring harness went all the way back to the ecu in the trunk, but it all just goes to the passenger footwell. So no splicing involved for this shielded wire, I’ll just wire it like it was originally.

Question for the guys with 3D printing experience: Might it be possible to 3D print connectors for NLA wiring harnesses? On the type where the metal terminals snap in, I’d think it’d be pretty easy – but you still need to source the metal terminals, unless you can 3D print those too. On the type where the connector is evidently molded around the connectors, perhaps trickier.

My exp making objects in cad is far greater than actually getting them printed, BUT I’d say that MOST of those connectors and pins are still available for purchase (the plastic ones). But yes, they could be printed -preferrably in nylon - or sent out to like JLCPCB 3D services for sintering nylon powder. The pins are usually cut and folded sheet metal - which is pretty precise. One could probably have that laser cut from thin metal (then precisely folded), but… I don’t think the trouble would be worth it vs just changing to an available connector.

The one execption I see here is those LUCAR silicon multi-way plugs with the bullet connectors. I’ve not seen any way to DIY those unless a 3D mold is printed for the harness and pins to snap into for a 2 pt silcon to be injected around.

~Paul K.

The only terminals I haven’t been able to find are the ones from the 9-way PM 4 connector.

Replaced with two 4-way weather pack connectors.

Got everything back together and the new wiring harness installed this past weekend. I did get an FF36 initially. The drivers side oxygen sensor wires were missing some insulation. I cut the wires there and put a new connector on and cleaned the sensor. That fixed the problem.

Other than that I had to reinstall the fuel injectors after one was leaking after install and replace a leaky radiator cap. It’s running really well now. Everything works except the AC at this point. Took it on a nice drive down to Salem from Portland yesterday.

Passed DEQ on Wednesday.

I don’t have pictures of the completed harness off the car as the last of the connections were made in situ. It wouldn’t be too hard to take off and I may at some point.

This is right before wrapping and putting on the car for final install. Still missing a few connectors.

Injector harness:

The wiring from the power modules and tdc sensor now runs along the left fender.

I relocated the relay from the radiator support to the right fender (the bracket was missing so the po had just glued it to the support).

The AC compressor wiring runs under the compressor and then over the valve cover with the fuel Injector harness.

Added grounding wires from the rear of the right intake manifold to the right side anti roll bar mount and one from the power steering pump mount to the left side anti roll bar mount.

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I believe the ABS connector on the XJ40 uses those if you need to nick a PM4 connector from somewhere. TE/AMP PN 343066-x Probably NLA:

~Paul K.

I made a few inquiries trying to find the pins for the PM4 and it does seem like they are NLA.


One other discrepancy between wiring diagrams and what I found on the original harness.

The shielding from the wire running to slot 24 has a jumper that runs to slot 7. Diagram doesn’t show this. I don’t know if this makes any difference, but I wired it up as I found it rather than to the diagram.


I think I jinxed myself saying that it was running well. I had it idling night before last, after returning from the 90 mile trip on the interstate, trying to locate a vacuum leak. It started overheating. The next day I took it out for a short drive to see if it was just lack of airflow causing the overheating and it continued to overheat. Going to check coolant level again, thinking maybe there’s air in the system. It is still running fine but temp gauge creeps up to within a needle’s width of red.


Vacuum leak seems to be coming from the air balance pipe connecting hose. Is that EAC2655 or EAC2654?

  • Forum directs you to 2654 but that’s listed on supplier’s pages as either “Water Bypass Hose” for XJS or “Cooling hose, bypass, pipe to manifold, V-12” for an E-type V-12:

    EAC2654JAG_1

  • EAC2655 is listed as “Hose, On Extra Air Valve” for XJS 76-96:

    EAC2655JAG_1

Looking at the shape and length I imagine either would work, diameter is what I’m unsure of.


@Kirbert I did see a video on Portland Wiring Harness’ facebook page showing their 3D printed connectors. Redirecting...

The issue with that air balance pipe hose is that you want something stout enough that it won’t get sucked flat. I have suggested marine coolant hoses, as some of those things are so tough you could use them to hammer a nail.

Yeah, I figured it would be obsolete. I did find the Mouser listing, but that doesn’t mean they could get any. https://www.te.com/usa-en/product-342545-1.datasheet.pdf They’ll probably have to be slavaged as pigtails from wrecked cars or switched for a different connector.

Interesting the extra unlisted ground.

~Paul K.

Working on rebuilding a wiring harness for someone. While looking it over I found that the Black/Pink wires that connect the idle switch, air temp. switch, the ignition ECU, and the strategy selection link don’t appear to connect directly to ground like shown in the wiring diagram. If I remember correctly, on the first harness I did, I simply ran them all to ground on the firewall.

Maybe there’s a jumper to one of the many ground wires from the ECU that is grounding this group of wires? Maybe it doesn’t matter?

This is what it looks like in reality:

Finished up the harness I’m making for someone today. Tested and working last night. To confirm it doesn’t matter which way the ground wires are wired that I noted in my last post. Strait to ground or just interconnected.

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