Smoke, engine bay wiring project, probably?

[shawn908]

The car was working fine, driving about 3/week - 100 - 150 miles/week. One day, out of the blue, cranks but no start. Read threads. Had a spare (new) DME, swapped it. Still, crank no start. Could not figure it out – so flatbed to the shop. They fix it with new part, cited as "ignition relay" ($100 part, I assume a DME). Also new spark plugs since “plugs were fouled by gas” due to cranking and no start. Paid for that and it ran great, drove it to work and back last week (45 miles). Shop also commented something like engine bay wiring needs to be cleaned up. Prescient as it turns out.

Few days ago, go for a 10 mile drive. One stop along the way for a java. Get home. Before shutting it off, check oil and add required 1/2 quart. Then finish heat “back date” project. Pushed around wiring in engine bay to install the orange hose, but only wires in very close proximity to the orange hose. Like spark plug wiring.

Then I get crank no start exactly same as before I had it flat bedded.

Start poking around looking for a loose connection. Open the connection box as indicated in the photo, noticed one lead unplugged – so test fit where it appeared to be from. For immediate result of that, see smoking engine bay. Disconnected everything. The smoke was burning wire on rear fuse panel. What have I done?

So many questions. Why did I have only 1 of the three fuses in place and the car worked fine? Why did making that connection fry the wire in the rear electrical box?

Should I make this the winter project and do a complete new rear harness and can the dodgy looking rear electrical panel be “upgraded” or replaced?

Thanks for any suggestions, comments or humor...

[pmax]

Ouch ! Sorry to hear about this.

Given the unknown condition of the existing hack job wiring even before the short, replacement of entire harness is advisable. If I were you, I wouldn't beat myself up too much about what you did. It was an accident waiting to happen regardless and better to have it in the garage than burn up your car om the road.

[sugarwood]

Which lead was unplugged?
And where did you attach it?
Maybe someone can post a photo of their correct configuration

[Techno Duck]

That rear fuse block always has 12v going to it. Its for the rear window defog, rear wiper and the engine compartment blower motor. If your car has no rear wiper and backdated heat, that would explain the other fuse missing.

The wire that burnt up is the ground wire, so whatever you connected was likely a 12v.

What color wire was the one you connected?

[3rd_gear_Ted]

Figure out the circuit routing and end function of each of the wires you mistakenly crossed up and go from there.
Determine by isolation the extent of short circuits to ground or each other wire in the wiring harness portion damaged. This is not an easy task and might not be feasible

[Norm01]

First suggestion is disconnect battery for now, there are live wires back there.

[pmax]

That relay panel is not original to the car.

I would remove it and see what's underneath. The 2 yellow wires in the pic, the wiring from the fuse panel should be going inside the panel.

Look up 3.2 conversion. Pzary3233's 78 SC 3.2 Swap Project

[shawn908]

Thanks for responses so far.
pmax - agree it was/is a hack job and now looking at it probably not suitable for the driving I like to do in the car. Although my (too blind) efforts lead to this - I’ll take the opp to correct. Also thx for the reference to Pzary3233 thread.

Norm01 - thx - disconnect was done immediately.

Others - I need to get back to engine to address, but I do want to retrace as much as possible to understand the basis for the hot lead that fried the ground wire in the relay panel.

[gerakroo]

Hi Shawn, just replied to your email, i'm sure we can help !

[proporsche]

from what i can see is that somebody mickey moused the el.plug and inserted some kind of a alarm or kill switch into the plug.What you did is connected that loose(red) connector to a ground wire.
The rear plate is not original to your 911 as Pmax said...Basically somebody messed up ...as said disconnect the battery..remove the el. tape and remove all non original wires--show us the picture of naked harness we will help you

Ivan
original panel

[shawn908]

After 3 months of looking at this damaged car, I flatbedded it to the local P shop. On one hand I could probably do the job with help from Pelican (has helped me several times previously) on the other hand, after 3 months if that is true why haven't I finished it? I know the answer...

The shop pulled the electrical and I'm now looking to replace as shown in photos. Going to Hershey to hopefully find one (if anyone has one LMK, would also pay for shipping, too). Shop is suggesting get a new loom bit, at least, as that is what I cooked.

A trusted shop is an old car's friend. I'm disappointed in myself for failing to fix it, but would rather work with the shop and get it on the road and trusted to be done right.

I do have a nagging feeling that I should just rip out the engine harness, plus (hello, Kroon...) and re-do properly... Maybe that's a next step after driving this summer.

[gazzerr]

Send it to timmy2. He'll rebuild it for you better than new and he's very reasonable.

[E Sully]

Unfortunately, your 2.7 to 3.2 conversion wiring needs a bit of work. It is hard to tell what was done on that electrical panel. I don't know if Kroon makes conversion wiring. Timmy2 may be able to help, I gave him some of my wiring info years back.
This thread may help It shows the panel I made along with some wiring info. There are some differences between 73 and 74 engine harnesses.
HELP Please! with another 1973 3.2L implant

[sugarwood]

Originally Posted by shawn908

After 3 months of looking at this damaged car, I flatbedded it to the local P shop. On one hand I could probably do the job with help from Pelican (has helped me several times previously) on the other hand, after 3 months if that is true why haven't I finished it? I know the answer...

Smart move.
The dumb move is to be in denial of reality and have the car sit until your death.
This is the all too common outcome, in most cases.

I have a rule.
If I have no fixed it within a month, I will never fix it,
and it time to punt it to a shop.
And I never feel bad about that, since the alternative is to have the car rot until my death.

[shawn908]

In conclusion (of this project), I was at Hershey with a mission this year - to find a replacement for the fuse panel/harness I errantly cooked. Systematically searched the rows asking vendors small and large (DC etc) - nothing. Although they could source the following week when back etc... Last row last, private vendor from somewhere up the Hudson in NY, had the attached. Was not in a great position to negotiate, the vendor tolerated my attempts - and I just bought it.

The local Porsche shop (excellent if anyone needs a recommendation for Philly region) had the car for a few weeks, and not only installed a new harness (salvaged from the Hershey purchase) between the fuse panel and the engine, but also identified some nasty wiring. I can't describe the entire mess but I can say it involved a nut, a bolt, multiple hot leads that bypassed the fuse box and floated under the drivers seat. How did I even live with that? Could not see it and until this crank no start issue - everything functioned. Now that the starter is correctly wired, including the fuse panel.... amazing how much better it starts. Live and learn.

Feels good to drive it again. Next project coming up....