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Avoiding electrical fires after a near miss?


Active Member
Feb 6, 2024
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new mexico
I just finished up my four barrel carb swap, I'm redoing it unfortunately to fix a manifold vac leak. I had the coil pack grounded to the intake, and I forgot to connect the temp sending wire. But the other day I went to move it, it was under powered due to the leak, but it shot a big plume of smelly smoke, the old electric choke wire (I just disconnected it at the spade north of the choke spring/wire assembly) is completely burnt, taking a few others in the umbilical sheathing. I want to completely remove the old choke circuit, and buying the same gauge and replacing the other damaged wires. I don't know how the gas pedal sends the signal to close the old choke Any advice welcome, I'd be heartbroken if this truck burnt.
The gas pedal is linked to the carb by a cable. No electronics.
The choke is inter connected by linkage on the carb. The choke heater slowly opens the choke , there is a spring in the choke heater, on which the wire heats up the choke to speed up the choke opening. The wire that powers it is branched off the "on with key on" circuit. I've done similar, when that choke wire came off my choke unit because it needed a little squeeze to tighten it in the choke terminal, and it ended up burning up a fusible link.
On my most recent 85 I got it with a train wreck of a wiring harness, I ended up finding another one in the junkyard and put the junkyard harness on mine, was the quickest easiest way to fix a lot of previous owner interference.
You are a legend! Thank you so much for this valuable advice. I believe my last question is, my truck is a weird 75-77 combo model, is there a period of years I can buy a wiring harness for and be compatible?
I'm not sure exactly, my current project is an 85, which is different from yours but back then there were several years where they didn't change much.
On mine there were several places where wiring was just twisted and crudely taped. The main hot off the alternator changed colors and gauge size 3 times in the length of the valve cover and had bare strands hanging out of the tape job.
Wire nuts have no place on a car or truck but even that would have been an improvement.
One of these crude splices was dangling 1/2" from the fuel line that comes over the valve cover from pump to carb.
I've also laid out wiring harnesses on the kitchen table and untaped em and cut out bad spots and replaced em before then retaped the whole thing and put back on.
I did that with my 85 and it's junkyard harness just to check for bad spots from age... Chipped insulation, corroded splices etc. and my way to fix is bare barrel splices crimped then soldered then the"good" marine grade heat shrink.
Then tape up the whole harness like original.
On the 85 I also modified my harness, as in getting rid of every fusible link under the hood, by adding in an under hood fuse box like newer cars have. I went back to the junkyard and looked at pretty much everything in the yard at what they had, and ended up with one that I cut out of a 90-92 ranger (yeah a Ford part in my Dodge) I wanted something fairly small but with enough fuse slots to cover as many fusible links as the truck has plus a few for future expansion.
I looked all over at available aftermarket fuse boxes and for general information about wiring, fusing, and such and I actually got ahold of the Littelfuse company, who sent me a service bulletin about the development of the maxi fuse which said it was created specifically to replace "fusible link technology".
And I pretty much figured out how heavy to fuse everything based on a combination of gauge size of wires coming out of a given amperage fuse slot, plus the gauge size of the circuit left once the link was cut off. I never really likes sending current thru a length of wire 3 gauge sizes smaller than the parent circuit. And a maxi fuse will be easier to find "anywhere" than any or all possible gauge sizes of fusible link wire...
So am I looking at just a wiring harness or harness + rebuilding the fuses like you? I was really hoping just a harness would do as this truck has been down a while and I want it back desperately.
As much as I want to just do the harness if the fusible link crap is a fire hazard im gonna replace it. Lastly how do I prevent the choke heater wire from getting hot as it did? Put the choke heater in place, put the wire to it and remove the steel wire to the choke arm so the wire isn't open and getting hot but it doesn't move anything?
On the choke heater wire didn't you say it became unplugged and grounded out?
On the fusible link thing you can probably get by cutting it out and replacing with a fuse holder crimped into its place, and well insulated (again the "good" heat shrink with the adhesive within)
You don't have to go to the extreme that I did.
And don't get caught up in the hype about "painless" etc wiring harnesses because well, they aren't.
The bigger hurry you're in, more chance of missing something, etc and the further problems this thread was posted about wanting to avoid.
Find a factory service manual for your year and follow the wiring harness compared to what you have and make them match, so NOT waste the money on Haynes, they are just about good for fire starter is about it, they suck.
You say your truck is a mix of 75 and 77, wouldn't that make it a 76?
On trucks I don't think there was much difference between the wiring between those years.
That harness should be pretty simple to trace and fix whatever ails it.
Do pull the plugs at the bulkhead (pass thru at firewall) and check all the terminals for corrosion. Clean good with contact cleaner, a little dielectric grease in there won't hurt.
I bought an exact replacement wiring harness, gonna cut the choke heater wire out and replace it.
It's not a 76, it has the single year clear vertical turn indicators of the 77, but the vin and motor of a 75
Maybe somebody changed the grill at some point? I wrecked my 79 when I had it, quickest way to get it back mobile again was to get the only parts I could find at the time and bolt them on which were '78 parts
They do so they must have changed the whole front end, the body under the grill doesn't even have holes where the indicators were, and I the original forest service yellow paint is all on the inside, it's really confusing.
They did weird things with "fleet" vehicles.but when I did the retrofit on my 79 I used the filler between the grill and bumper that came off the junkyard refugee, I believe I might have had to extend the parking lights light socket wires but that's been 30 years ago I've slept since then.
If I could find a decent one, id like to see if I could find a 72-73 grill and see if I could see if I could make it fit my 85 "like it belongs there" since I also have a 70s birdbath hood