started as wire fire, now Djet electrical questions, injectors are not firing Options

[brant]

So last fall at the RRC event in October I had a wire fire in the front trunk area
Specifically, the wiring under the fresh air system
I've been procrastinating on tackling this job for 9 months basically

I found a single burned wire that had wore through the insulation, shorted, and then melted the insulation for 3 feet. This wire was one I had added 20 years ago for an auxiliary oil pressure warning light (it was not in any factory loom luckily)


That wire is replaced
all wires crossing, or touching that wire were inspected.
Obviously, I've missed something


The car drove home, and at that time all systems functioning except for the cig lighter, horn, and an auxillary oil pressure warning light (the actual item that shorted)


Now, after pulling the tank, replacing the wire, and inspecting everything...
the problem has worsened. The starter will not turn over, the fresh air blower is not working, plus the horn and cig lighter are still dead, no fuel pump power either (relocated to front trunk) more systems now impacted than initially

I dropped the fuse panel
all of the fuses are intact.
5 of the circuits have power (coming in, and exiting those fuses)

the remaining (is it 6?) circuits are completely dead on the fuse panel
no power coming into the fuse, whether the key is switched on or not

can anyone tell me where the multiple powers supplies to the fuse panel should be coming from? (the 5 working circuits are switched with the ignition key)
I know that is too broad of a question, I will identify which circuits are dead once I look at the diagram


its a 1974

sorry I hate wiring
I will get out the diagrams today
but would love any idea's or brainstorming from anyone that's experienced similar


TIA
brant

[Superhawk996]

@brant

I usually try to avoid answering electrical questions since too many are looking for the easy solution and group think answer.

As a former USAF electronics tech I can safely say that what you need is a Digital Multi Meter, the schematic, and a lot of patience. You can and will solve this. It is not hard in a technical sense but it is HARD to have patience and to follow a methodical method.

Where this method usually fails is that you start out methodically, and then THINK you've found something (potentially unrelated or inferred by guesswork) that leads you off on a goosechase. The only sane course of action is to return to the methodical appoach and to see it though. When technique is used methodically, you will be successfull.

USAF teaches this method because it works and is the fastest way to get a system up and running under pressure.

The link below is how to use the 1/2 split method to locate the issue quickly and reliably.

http://www.914world.com/bbs2/index.php?showtopic=337270

[brant]

Thank you.
and I'll buckle down tonight!

half split method!

[brant]

updates...
and I think I need to start working on the Djet now

I previously replaced the burned wire (not stock) that I was using for power in the front trunk to an oil pressure aux sensor. but after that repair found wipers, starter, cig lighter, horn, fresh air fan all to be dead

One by one I've been working on these. I found the horn relay to test bad, replaced that and fixed my horn

I found the main ground on the back of the cig lighter to have come off. tightened, cleaned, and replaced. Fixed the fresh air fan, wipers, cig lighter, and now the starter is activated/hot when in the start position (I'm guessing a ground in the column/switch was keeping the starter circuit from running)

but Now I have another symptom I didn't know about
and again... it doesn't make sense to me... This car drove into the garage in October after a 500 mile day.

Now that all of the interior items are working
and the fuel pump is running
the starter is spinning.
but the car will not start


And... 6 of the fuses are not hot when the switch is turned on
it is the 6 fuses on the outboard of the fuse board

does anyone know if these are powered only when the car is running
I honestly don't know, never checked or noticed previously


I have fuel
I have spark
the noid light shows none of the injectors are receiving any signal

I tested the 4 relays on the board, and they are all working. that circuit is hot all of the way to the T12

I checked the 3 wire connector at the distributor. It looks good. and the center wire has continuity to all 4 injectors when I use my ohm meter

my electrical diagram is a Haynes manual that has been printed too many times. I can't make out the regulator board circuit to the 4 white wire FI connector on the back


does anyone know those 4 circuits that feed the ECU?



or how to test the distributor FI points in the bottom of the unit?