Landseer

Thanks for the responses. Good advice. I had started down a bad direction, thinking I could ignoring the harness burn through as unrelated. Its the starting point.

CE PANEL
Dropped it with 2 screws, then pulled plug-ins and removed CE.
CE is on dining room table where I have light.
So far, I see no damage at all among wires on reverse side of CE, even those that feed "F" plug. They are all pretty heavy wires. Will look very closely again tonight with a pick and magnifying glass. Terminals are well-fitting and don't appear corroded on back---am inclined to pull and clean all, though. I have a couple new packages of fuses and the diagrams to fit the right ones for the 84. Will polish fuse holders first. Garrett, your wires must have gotten awful hot. Same harness, as you indicated too.

F PLUG-IN
Under dash, looking at plug-in wires, the fried wires and damaged wires seem isolated to "F" Plug. Worst is top left brown or red wire exiting plug (three actually exit at that terminal). Others seem collaterally cooked, at least with respect to this end of the harness / gotta find the cause elsewhere. I'm guessing these are bundled and form at least part of the "headlight" harness. Seems like wires are arranged at certain plugs to purposely form a logical distribution network.

COOKED GROUND WIRE
Again, yesterday's pics, one ground wire is completely cooked. Its a ground above CE, on a bolt to right of the ground bolt that grounds CE to body. Will Need to pay special attention to tracing this. Not sure if it is associated with F Plug-in or if it will send me on a parallel adventure.

S PLUG-IN
In pictures above. On a couple of two-color wires exiting S-plug, some deterioration there, seems isolated to the few inches leaving panel, but is noted for later trace.

UNDER HOOD
Damage seems concentrated in that main right side harness. The 14 pin feed emerges in a sub-bundle from that harness. The burn-thru sheathing continues further past that point, towards the front of car. Will trace further tonight and look for body/wire shorts and other problems --- need to find the "causal" part or at least uncover all the damage. This harness does loop around the nose and feed coil as Jim recalled, including resistor pack. So much for my original logic. So the harness is much more than a headlight harness.

Saw no damage on entry/exit to 14 pin. Need to dissasemble and inspect more closely.

Thank you for helping me attack this logically. Got some wire tracing to do yet. Maybe my brain will be ok. At least let me believe it for the time I'm at work today...

Mrmerlin

jack up the car remove both front tires and remove the front portion of the inner fenderwell block off plates, most of your problems will be found under either fender, pay careful attention to the headlight harness as it comes from the headliht to the anchor point on the fram horn this where I have found most of the headlight shorts usually the harness is clamped with not enough extra cable so it can flex and thus it begins to flex at the clamp and eventually shorts out

Landseer

Got it. Going up tonight, will snap a few photos. Thx. CT

Landseer

I think I've got it,

Side marker light wires.

Rub-thru and unmistakeable contact with body near radiator on right of car as harness crosses to feed driver's side.

Melted insulation and bare wires throughout front area.

Will continue to trace rest of wires.

Thanks Mr. Merlin, aka wizard in these parts.

Jim bailey - 928 International

Good job sorting that out. Once you get the crispy bits isolated you can get back to the issue of power to the coil . As test you can temporarily jump from the jump start post full 12 volts to the # 15 positive terminal on the coil but only for a short time as the coil was designed to run on less than 12 volts and can over heat and boil the oil .... The 78-84 cars use two resistors to reduce the power to the coil. When cranking on the starter power flows only through one but in the normal running mode must pass through both.

Landseer

Thanks, that's going to help in the next step.

I performed exploratory surgery on parts of the harnesses. Looks like side marker wires shorted in one of a couple possible places. PO replaced 8A with 16A. Result, carnage. Melted into various wires, here and there, in engine harness. (Cause or damage might also be in right rear harness for parking lights.) Am suspicious of driving lights, too, where the harness splits from side markers. Hard to know what caused what.

Looks also like PO had a horn problem. My melted red wire at F plug-in, and into dash harness, traces in fuse box to output from horn relay. PO replaced 16A with 25A. Horn wires run bundled with side marker wires. But this melted wire runs under dash in big bundle, presumeably to steering wheel.

Burn marks at fuse 18 relate to rear defroster and/or mirror heaters according to panel charts. That I can do without for now. Maybe horn wire caused it. Hard to see. Don't want to remove dash, gotta get scope under control.


I hope to focus this weekend on isolating and inspecting wires related to engine management, hopefully staying in engine compartment.

Need also to confirm and troublshoot what appears to be shorting at injectors.

Jim bailey - 928 International

Stupid, stupid ,stupid....."PO replaced 8A with 16A. Result, carnage. ... also like PO had a horn problem. My melted red wire at F plug-in, and into dash harness, traces in fuse box to output from horn relay. PO replaced 16A with 25A...." If a fuse burns out it must have been too small ? What kind of idiot must one be to think that !!!! The REASON for a fuse is to protect the wires !!! bigger fuses (higher amps) protect bigger wires and turn small wires into a toaster.... But it was a cheap fix !!! Sorry to hear this Chris. Might be good for other people to CHECK ALL THE FUSES in their car. We have fuse and relay charts in the store in the Tech tips section...

Mako 928

Sounds like PO is one generation away from the "Heck if the fuse keeps blowin just jam a penny in there" Some things never change.

Landseer

Update & need a bit more guidance.

Removed CE, polished all plug connections and relay tabs and fuse holders. Replaced all fuses with proper value. Reinstalled. Looks good. Cleaned-up some speaker wire splices and removed stereo install hot lead.

Ran new wire for right front parking lights + a spare.

Unplugged and removed wiring harness, starting at coil + resistors, from left of car, around to right, removing all lighting connections for inspection. Damage limited to one pinkish red wire carrying marker and maybe driving light voltage. Ran a new wire from CE to front right as a patch in a sheath.

Checked resistors. I'm a bit electrically challenged, but digital meter shows 6 + 8 ohms (instead of 4 + 6 ohms). Is this ok?

Am simultaneously cutting-out and replacing injector harness, due to continuity across plug and to ground. Here is where I am getting confused. Cut-out drivers side pigtails --- all were fine, no fray.

Still getting continuity from one lead to ground on remaining injector pins. Does my X plug need to be disconnected to run this check? No continuity if X-plug is disconnected. At CE, have continuity between lower right X plug male and several down the left side. Have troubleshooting CDs ordered, but can somebody help me through this injector wire confusion?

ZEUS+

Yes the X plug must be disconnected to properly test circuit along with all injectors.. The injectors are batch fired. The LH pulses a ground signal to each bank of injectors.