76 Bronco backfired and died while driving, now there is no power

[jamesahughes40]

76 Bronco backfired and died while driving and would not restart. Since then, have replaced coil, fusible link, solenoid, battery wires, ignition module, and still nothing. No power to headlights, horn, or anything when the key in ON or ACC. Nothing happens when I turn the key.

 

[73azbronco]

battery voltage?

voltage at starter relay?

Voltage on hot side of starter relay when key turned to run or start?

 

[DirtDonk]

Also check under the dash at the back of the ammeter. There’s a push together bullet connector that might be deteriorating, or might have separated.
It’s a longshot maybe, but if that connector comes apart, nothing in the vehicle will work.

In most cases like this (similar but not exact) though, the loss of power is one of the battery cables.
However, they don’t usually kill the engine while it’s running. Just keep it from starting later.

 

[jamesahughes40]

battery voltage?

voltage at starter relay?

Voltage on hot side of starter relay when key turned to run or start?

Voltage at battery is a tick under 12. None at coil. I will have to check relay.

 

[jamesahughes40]

Also check under the dash at the back of the ammeter. There’s a push together bullet connector that might be deteriorating, or might have separated.
It’s a longshot maybe, but if that connector comes apart, nothing in the vehicle will work.

In most cases like this (similar but not exact) though, the loss of power is one of the battery cables.
However, they don’t usually kill the engine while it’s running. Just keep it from starting later.

I thought cables originally too. But I replaced them, cleaned posts, and still nothing

 

[DirtDonk]

It has nothing to do with the starter relay. Your battery is connected directly to the cabin power by the black wire that you say you replaced the fusible link on.
It’s a direct connection on that stud, so there’s nothing inside or external to the starter relay that can break that connection.
Maybe the new fusible connection is faulty. Got a picture of your layout?
Do you have an upgraded alternator on your bronco? If so, is it running through the original wires?

 

[DirtDonk]

And unfortunately, while extremely rare, there’s nothing that says brand new battery cables can’t be faulty too.
New parts are horrible in general, but also in general, new battery cables are usually perfectly fine.
However, there are plenty of members here who have had bad experiences with auto parts store bought cables. I’m not one of them however, ans all of the ones I bought have been stellar save one. And that one at least lasted a few months. Almost a year maybe, before it failed catastrophically and gave me exactly the same symptoms you have trying to restart.

It wouldn’t hurt to maybe do a voltage drop test or something. But right now my money is on the main black power wire.
With the new cables, do you have a ground cable connection directly to the engine, and also one directly to the body?
Have you ever added an additional ground cable between the back of the engine and the firewall?
Just checking to get a basic mental layout of your set up.

 

[jamesahughes40]

And unfortunately, while extremely rare, there’s nothing that says brand new battery cables can’t be faulty too.
New parts are horrible in general, but also in general, new battery cables are usually perfectly fine.
However, there are plenty of members here who have had bad experiences with auto parts store bought cables. I’m not one of them however, ans all of the ones I bought have been stellar save one. And that one at least lasted a few months. Almost a year maybe, before it failed catastrophically and gave me exactly the same symptoms you have trying to restart.

It wouldn’t hurt to maybe do a voltage drop test or something. But right now my money is on the main black power wire.
With the new cables, do you have a ground cable connection directly to the engine, and also one directly to the body?
Have you ever added an additional ground cable between the back of the engine and the firewall?
Just checking to get a basic mental layout of your set up.

New Ground is directly to engine, none directly to body though.

You’re saying though that the black wire with fusible link connect directly to cabin? It also has a yellow wire spliced into it. Maybe I’ll try following that and see if it’s broken/corroded/disconnected. Thanks

 

[73azbronco]

if you are under 12v, your battery is officially dead. Or, the cables and connections are bad. But even bad connections will give voltage readings correctly, just not flow power.

Remember you are into ancient tech, where back in the day, we replaced everything at 5 years just to be sure, battery, cables, points, plugs wires, hoses, all of it. But that was when battery lasted 5 years, not 2.

 

[jamesahughes40]

if you are under 12v, your battery is officially dead. Or, the cables and connections are bad. But even bad connections will give voltage readings correctly, just not flow power.

Remember you are into ancient tech, where back in the day, we replaced everything at 5 years just to be sure, battery, cables, points, plugs wires, hoses, all of it. But that was when battery lasted 5 years, not 2.

Unfortunate since I just got this battery about a year ago….

 

[DirtDonk]

New Ground is directly to engine, none directly to body though.

Definitely need one to the body.
You can often get away without it, but not efficiently.
Best to supply at least one body ground. If not multiples. Modern vehicles have multiples. And by “modern” I mean anything after 75.
Unfortunately, Broncos didn’t fall into the, “let’s update them along with everything else” category as far as Ford was concerned.
They just left us with the bare minimum.

You’re saying though that the black wire with fusible link connect directly to cabin? It also has a yellow wire spliced into it. Maybe I’ll try following that and see if it’s broken/corroded/disconnected. Thanks

Yes, exactly.
The yellow wire that splices directly into it is the alternator sensing wire. Goes directly to the voltage regulator on the original external type.
The big black wire is the main “loop“ that runs literally from the alternator output, through the firewall, powers everything under the dash, and then back out of the firewall to the battery, to keep it charged.
So even though you can disconnect the alternator and everything will still work, you can’t disconnect the end at the starter relay.
Do that and nothing works.

Same for if that connector at the ammeter is disconnected. It’s the same wire.

 

[m_m70]

Unfortunate since I just got this battery about a year ago….

Have you tried to charge it??

 

[Madgyver]

distributor rotor turning?
Pin sheared?
gear worn?

 

[Speedrdr]

Something like ^^^ as @Madgyver eaid leads me to think any of these could be the issue, plus the cam chain maybe jumped a tooth or two causing it to jump time. I would lean towards something along these lines as to why no firing.

Randy

 

[m_m70]

76 Bronco backfired and died while driving

This seems to go with

distributor rotor turning?
Pin sheared?
gear worn?

This. Mine did this when the shear pin broke. Just a quick backfire and died.

No power to headlights, horn, or anything when the key in ON or ACC.

This seems to go with

Your battery is connected directly to the cabin power by the black wire that you say you replaced the fusible link on.
It’s a direct connection on that stud, so there’s nothing inside or external to the starter relay that can break that connection.

This. There was just a thread on this in the last couple months. I'll try to find it.

Nothing happens when I turn the key.

I'm assuming that "nothing" means nothing. No turning over, no clicking, no nothing. My Bronco has always been a manual transmission but my brother runs a c4 in his and every time this has been an issue in his was the NSS. Either the switch gone bad or out of alignment.