Did I fry something messing with my ignition?

rednotch · Oct 20, 2025

Too much digging. The wires jumped on an AOD vs t5 for ngs by the pedal box if I remember correctly. De pin it from the ignition switch and test at the terminal at the switch, if the terminal isn't seeing full voltage there's your issue. I do not at all miss doing that for flat rate .

85gtCOBRA · Oct 20, 2025

rednotch said:
Too much digging. The wires jumped on an AOD vs t5 for ngs by the pedal box if I remember correctly. De pin it from the ignition switch and test at the terminal at the switch, if the terminal isn't seeing full voltage there's your issue. I do not at all miss doing that for flat rate .

I think I get it. De-pin (disconnect) wire from ignition switch, test at terminal, key on. Same result with wire out of the equation, ignition switch is the problem.
I'm a layman - just want to make sure I get it right.
Were you a dealer mechanic? Would this be given to you as a "no-start"?

85gtCOBRA · Oct 21, 2025

85gtCOBRA · Oct 21, 2025

not liking this. testing at start signal (red/light blue wire) terminal of the ignition switch (wire de-pinned) ... nothing.

Kind of hard to know if you are making contact, you're doing it blind. Tried a bunch of different ways; probes, pins, pieces of wire, you name it.

for the hell of it, i touched the de-pinned wire with the multimeter ... wtf?
same voltage i see on the wire going to the starter solenoid, same voltage i see on the wire at the TFI module (2.27).

voltage goes up if I put the trans in gear (forward or reverse)

rednotch · Oct 21, 2025

Back feeding voltage, that's going to be fun, you all ready replaced the coil right or at least disconnected it while testing?... That wire runs to the pedals, Aod should be a jumper plug in that area, trees off to the trans harness, starter relay and tfi, don't remember any other power source tie in but don't have an evtm.. Your getting the crank signal from it still to the relay if engine cranked so switch maybe intermittent or just didn't get a connection when probed. So not looking like the switch.

You replaced the coil all ready right, or at least tested with it disconnected? What exactly did you tap for the tach signal and did you see any evidence of melted wires, smoke, etc or just not starting after. If the coils been replaced its time to start tracing wires.

Fox bodies my rule is all ways have a spare good loaded Distributor on hand, even coils these days because alot of the old wiring will kill them pretty quickly on these cars, many need harnessess repairs in the engine bay but alot of people just throw parts at it instead.

The post jricker has on here might help a bit. https://stangnet.com/mustang-forums/threads/blowing-pip-sensor.923570/#post-9350134

85gtCOBRA · Oct 21, 2025

rednotch said:
Back feeding voltage, that's going to be fun, you all ready replaced the coil right or at least disconnected it while testing?... That wire runs to the pedals, Aod should be a jumper plug in that area, trees off to the trans harness, starter relay and tfi, don't remember any other power source tie in but don't have an evtm.. Your getting the crank signal from it still to the relay if engine cranked so switch maybe intermittent or just didn't get a connection when probed. So not looking like the switch.

You replaced the coil all ready right, or at least tested with it disconnected? What exactly did you tap for the tach signal and did you see any evidence of melted wires, smoke, etc or just not starting after. If the coils been replaced its time to start tracing wires.

Fox bodies my rule is all ways have a spare good loaded Distributor on hand, even coils these days because alot of the old wiring will kill them pretty quickly on these cars, many need harnessess repairs in the engine bay but alot of people just throw parts at it instead.

The post jricker has on here might help a bit. https://stangnet.com/mustang-forums/threads/blowing-pip-sensor.923570/#post-9350134

85gtCOBRA · Oct 21, 2025

Thanks for getting back to me.

Yeah, found it odd that I wasn't getting anything at all at the switch. Hard to know if you're making a connection there, you're totally blind. Believe me I tried. If there was in fact nothing coming out of that terminal (along with the 3V on the wire) would that add up to something?

Have not replaced the coil. Yes it was disconnected while testing. Also disconnected at solenoid & distributor.

No flash, no smoke, no smell, no melted wires (that I can see), no obviously cooked fuse links.
I tapped in to the back of the coil connector for the tach signal but i'm assuming something was done wrong.

It's not even like the car shut off while i was in the middle of it. Gave up on it (couldn't make it work), shut the car down, disconnected everything ... and it wouldn't start back up. Nothing spectacular. One minute running, next minute it wouldn't.

Mea culpa - I reversed polarity jump starting a car once ... dumb mistakes happen. Got lucky on that one.

Owned four cars with the 5liter, never once had an ignition problem so never felt the need to keep a spare distributor around. (2 of them were carbureted though). One habit I do have is keeping a spare starter solenoid around (which I do have).

Read that jricker post about 30 times in the last week.

Going to unplug the neutral safety switch and see what happens.

85gtCOBRA · Oct 21, 2025

Well, getting at that switch is pretty much impossible without a hoist. F*ck me

85gtCOBRA · Nov 15, 2025

Problem solved. Dropped in a new distributor and it's good to go

rednotch · Nov 15, 2025

So the pip failed, thought you tested that and the tfi in the other thread. Rebuild it, keep as a spare, the new China sourced ones are pretty crappy.

85gtCOBRA · Nov 15, 2025

rednotch said:
So the pip failed, thought you tested that and the tfi in the other thread. Rebuild it, keep as a spare, the new China sourced ones are pretty crappy.

It's an OEM FORD distributor out of the exact same car - So I know the gear is the right one. Dirty, nasty, sitting on a shelf in a scrapyard in Quebec for the last 25 years. Took it apart as far as i could, cleaned it up, put fresh thermal paste on the back of the TFI module ... tested it first before I dropped it in and got spark (and injector pulse). Pulled the one out of the car and did the same test ... stone dead. Dropped it in, car fired right up. timing was only off by a few degrees so i nailed that too. Might just be me but i swear the car is running smoother than it has for a while. Started up with more "authority" as well. Could be that OLD Motorcraft module that came with it.
The one on my car was a replacement, this is the proper one with the MOTORCRAFT molded into the plastic.
I will be rebuilding mine to keep as a spare.

Did I fry something messing with my ignition?

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