My new wiring harness

[flightlead404]

Made up a new ignition harness, all mil spec Tefzel wiring in fire/chemical/abrasion resistant fiberglass "snake skin" expandable sleeve, and double-wall adhesive lined heat shrink. Also re-dressed what remains of the existing wiring harness. Removed most of the old brittle brown tube and replaced with sleeving. Where I couldn't get heat shrink on the existing connectors I used self-amalgamating tape, hope it holds. I made some custom shroud plugs to use the same hold-down points as the original harness. I think it looks good.

[slyguy]

That looks great. How about black zip ties though What are you using to fire your COP?

[puddy]

Looks great! Where do you source wiring harness stuff? I'm going to be doing some myself soon.

[quattrorunner]

Purdy

[flightlead404]

I'll probably have to move some wiring around when I put it back in the car. I still have to build the sensor harness for the Microsquirt, so maybe I'll be anal enough to buy some black zip ties Actually I'll probably replace with proper waxed lacing cord. I hate zip ties (as I think I've mentioned before lol)

I typically go to prowireusa.com for that sort of thing. They have mil spec wiring in all sorts of colors and with stripes etc. They probably have the correct colors to remake a complete engine harness in Tefzel. I've thought about it, but never pulled the trigger. They can also print on the insulation if you want it labeled, something I've never taken advantage of.

For the COPs (I bought the non-Toyota branded Denso COPs) I'm using 3-conductor shielded 18 awg wiring. In that harness bundle is also a 16 awg ground lead that is bolted to the stud where the air pump used to mount.


I'll bring engine ground back to a terminal strip on the rear electrical panel where I'll mount my Microsquirt, fuse block, relay, two MAP sensors (one for MAP one for continuous barometric adjustment), and an EBC solenoid. That strip will have +12v ignition power, Spark A, Spark B, Spark C, +5v Vref, sensor ground and engine ground. The shields for the ignition leads and for the crank position sensor leads will be grounded there as will the Microsquirt and anything else that needs an engine ground

The plan is to use the existing delayed ignition relay to power a second relay delivering +12v to the ATC-style fuse block. I have not decided whether to bring a new power lead from the battery via the starter motor connection and a fuse, or pick it up off the original 3-fuse block off the rear electrical panel. Comments invited on that.

I can have the Microsquirt, eWUR, lambda valve, and ignition power separately fused on the block.

If the Microsquirt can't handle the current requirements for the COPs in a wasted-spark configuration it should be relatively easy to add a PNP power transistor to each ignition output with the COP as a low-side load.

['76 911S 3.0]

Looks good, my only comment would be to remove the paint on that bracket where the ground ring terminal attaches, want to make sure you have a nice clean contact point.

As far as +12v feed, I did as you described where I ran a new wire from the starter to my EFI fuse and relay panel to power all the EFI electronics.

[flightlead404]

Originally Posted by '76 911S 3.0

Looks good, my only comment would be to remove the paint on that bracket where the ground ring terminal attaches, want to make sure you have a nice clean contact point.

As far as +12v feed, I did as you described where I ran a new wire from the starter to my EFI fuse and relay panel to power all the EFI electronics.

Where did you fuse it? I was looking for a location close to the starter to mount a single 30A fuse but don't see a good location. The wire is unfused from the battery to the starter as I recall, so I'd like a fuse as close as possible to the starter

[slow&rusty]

Lovely work!

[flightlead404]

Originally Posted by slow&rusty

Lovely work!

Thanks!

It turned out I had to rebuilt the entire thing. When I was looking at the pics closely I noticed little nicks in the wire insulation. I looked at the wires themselves and started bending them, sure enough the nicked insulation opened right up.

Turned out the clamping part in my expensive automatic stripper was digging into the insulation, ended up redoing it with a rusty old stripper from the bottom of my tool box.

ah, strippers. Sometimes they're more trouble than they're worth!

['76 911S 3.0]

Originally Posted by flightlead404

Where did you fuse it? I was looking for a location close to the starter to mount a single 30A fuse but don't see a good location. The wire is unfused from the battery to the starter as I recall, so I'd like a fuse as close as possible to the starter

The large wire feeds a power panel like this (there is a single lug on the back that buses all the power to one side of the fuse):



This has all the fuses and relays integrated into it.

[9dreizig]

Just curious how are you making the splices ? Solder , crimps ? More pics please as I'm about to undertake the exact thing..

[flightlead404]

Originally Posted by '76 911S 3.0

The large wire feeds a power panel like this (there is a single lug on the back that buses all the power to one side of the fuse):



This has all the fuses and relays integrated into it.

ok, where is that buss mounted? I assume not near the starter?

I'm talking about the power take off from the starter motor terminal, which is unfused, which I assume feeds that buss. I used a couple of very similar ones in my airplane and there's no fuse on the feed, only the loads. So you have a relatively long run of unfused wire. I'm personally not super comfortable with that. If that wire chafes or otherwise shorts out before the buss you've got a potential fire hazard.

Circuit interrupting devices (fuses, breakers) are there to protect the wire, not the load.

Am I misunderstanding you?

[flightlead404]

Originally Posted by 9dreizig

Just curious how are you making the splices ? Solder , crimps ? More pics please as I'm about to undertake the exact thing..

Which splices?

The COP connectors use a crimp on terminal. I'll use a quality PIDG crimp ring terminals on the other end. Other connectors are weatherpack connectors. If I have to use a butt splice, which I'll have to do for a few of the leads as I bought a pre-populated Microsquirt harness, again I'll use a quality mil spec PIDG crimp on butt splice.

[9dreizig]

Originally Posted by flightlead404

Which splices?

The COP connectors use a crimp on terminal. I'll use a quality PIDG crimp ring terminals on the other end. Other connectors are weatherpack connectors. If I have to use a butt splice, which I'll have to do for a few of the leads as I bought a pre-populated Microsquirt harness, again I'll use a quality mil spec PIDG crimp on butt splice.

Thanks Yes I was wondering about the MS harness.

Once again you're my hero,, going to order my MS shortly and jump in

[flightlead404]

Originally Posted by 9dreizig

Once again you're my hero,

Too much pressure man, not sure I can handle it

[flightlead404]

This is what I ended up with. An in-line 25A ATC fuse right at the take-off from the starter motor/alternator B+ lead/battery wire, 14 AWG mil spec Tefzel wire, run through the sheet metal with the original harness, then a couple of -2 Adel clamps to route the wire into the harness.

There will be another larger Adel clamp on one of the shroud combination screws when I get the sensor harness build.





I also modified my rear sub-panel to get some more real estate. Not the best fabrication job I've ever done but it'll get the job done.

[9dreizig]

where are you putting the MSquirt ? Under the seat ?

[PhantomBlot]

Nice work on the harness. I like does 3d printed tie-down plugs. Would you share the STL files?
Did you print them in PLA?

[flightlead404]

Originally Posted by 9dreizig

where are you putting the MSquirt ? Under the seat ?

Nope I extended the rear electrical panel as shown above, everything will mount on there. I just got back from EU and plan on putting that together this week.

[flightlead404]

Originally Posted by PhantomBlot

Nice work on the harness. I like does 3d printed tie-down plugs. Would you share the STL files?
Did you print them in PLA?

Printed in TPU. PLA won't work because it needs to be flexible, and PLA wouldn't stand up very well in that environment either. At the moment I'm unsure whether the TPU will. I think it will be ok, but need to get the engine running to be sure.