The smell of electrical fire in the morning

[broncoluv]

Got up this morning, walked out onto the back deck to a nice blue sky. Cup of coffee in hand, talking to the little lady, i notice a funny smell in the air. Suddenly, i see thick white smoke begin to roll out of the engine compartment of my bronco! I rush over, throw up the hood, and see my msd6 box literally boiling! Yank the ground off the battery and it slowly stops boiling. It has been raining and the EB hasn't moved in four or five days! WTF!!?? I hate to think how bad thir could have been if it had went even fifteen minutes later, no one home all day. Adrenaline in the morning!

 

[Bronco Junkie]

Wow, that was a close one. Good thing it happened when it did. That is freaky..but I have a feeling there will be several other posts here with similar stories.

 

[broncoluv]

That is the second time an msd has gone bad on me, although the first just went bad it didnt catch fire. I am done with msd.

 

[TAC]

Wow frightening. Good you caught it!

Hopefully this isn't taking over your thread but anyone know of a list of the most common causes of bronco fires? I know gas leaks and electrical, but I am thinking more specific things to watch for that are most common. Some could occur when the bronco is parked like in your case or when the bronco is running. I have searched the site and see several fires discussed, but a tech article or specifics from a guru?

MSD ignition, fuel line leak due to age or ethanol degradation, PO drilled a hole in the top of the gas tank, the duffinator, the fortibis pin...?

 

[SDlivin]

I believe I have heard of 1 other story on here where that also happened.

Did you have a fuse inline between the battery and MSD box, or straight shot?

I know the instructions say run straight to battery, but I always thought a fuse was a good idea?

now that I just read this, got me paranoid, I'll be leaving work now.....

 

[broncoluv]

No inline fuse, but the hot lead to the msd box was handling the amperage well, its coating is intact with no visible signs of melting. Maybe a fuse would have helpf, not sure. Seems im in the market for a new ignition, maybe a new distributor with integrated ignition? Anyone have anything to say good or bad? I need to get rid of my old distributor anyway .

 

[EFI Guy]

Wow, glad you caught it in time!

Another good reason to fuse EVERYTHING.

As for new ignition, my only carbed vehicle runs a Duraspark dizzy, GM HEI module (well hidden), and Ford TFI coil. Never a hiccup.

 

[Steve83]

FUSE!!!! It doesn't ONLY protect the wire from chafes/cuts/pinches; the main purpose of a fuse is to protect from exactly this - an internal electronic failure. Remember the ongoing recall on Ford cruise switches? Same thing. If they had just put a fuse on that circuit from the factory, they'd have saved million$ (possibly Billion$), and more than a few lives.

 

[Jdgephar]

I hate to tell you guys this, but a fuse doesn't automatically protect from this. A fuse only protects for currents that are higher than the fuse is rated for. 10 amps of current can boil water on a faulty connection, but not blow a fuse. Now, I will never argue you out of running a fuse on a circuit connected to the battery, but be aware that fuses do not protect from all high temperature conditions due to a faulty connection. I'm sure there are others that have seen overheated connections for fan switches, headlights, etc. that burn the connector, but do not open a fuse.

 

[Steve83]

Sure, but we're talking about a fuse properly-sized for that ignition module & coil. Not a 30A...

 

[DirtDonk]

I wonder if they list what size of fuse would be good to use there? They supply very large gauge wires for those two connections only (10 ga maybe?) so seem to expect some decent amperage to pass through there during normal use.
But still, it took a fair bit to build up enough heat to melt the potting material and a few other things on that module. So I would expect some nominal size fuse to do the job.
What, maybe 20 amps?

Dunno, but I'll be checking out their data to see if I can find it. And do the same thing in my dad's car. Even though the battery is usually out, it's not always out!

Paul

 

[SHX669]

When you guys figure it out would you post up the solution/ method to prevent burning up the 'MSD box" . I've got a buddy who's melted two of the msd6 modules - kinda kept me from installing one till we find the cure.
SHX

 

[Steve83]

It would be a lot easier for someone with a WORKING box to simply measure the current draw, and post up. Maybe several people. IDK much about MSDs, but if there are several systems, be sure to post the model you're measuring, and under what conditions. Age of the system (since installed) & other things tied to the circuit (DOWNstream of the ammeter) would also be useful info.

The stock ignition system fuse in my truck is a 20A, but I'm sure that's somewhat oversized.

 

[jw0747]

best thing would be to toss the MSD junk and install a Duraspark system. cheap and easy to install and bulletproof. components available at most auto parts stores. MSD is okay for racers who run occasionally but not for a d.d. ask me how I know...

 

[SDlivin]

from msd tech section on a posting from a customer with a similar 'burnt' box scenario...
earlier in the thread, customer burnt up 2 boxes back to back. MSD tech points to possibly being a wiring issue external to the box....


http://www.msdignition.com/forum/showthread.php?t=6315

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It would take 30 amps to pop the breaker you put in. The box only draws 1 amp per 1000 RPM so if it only took 20 amps to burn the box up it would never pop the 30 amp breaker. Make sure also that the breaker is a DC circuit breaker and not AC. I am not trying to pass the buck by saying it is the car, it is just uncommon that there is back to back failures like that. We can get the unit in and look at it and try and point you in the right direction as far as why it failed. Let me know what you want to do so we can get you taken care of.

Thanks,

MSD tech4

 

[Jdgephar]

Sure, but we're talking about a fuse properly-sized for that ignition module & coil. Not a 30A...

Steve, it doesn't take much current to melt a plastic connection. 10 amps through a poor connection, lets say 0.5 ohms, is 50 watts at the poor connection. You can catch plastics on fire with 5 amps running through a poor connection (cheap plastics with no flame retardant). That's why most high current connections will have plastics with a high flame rating. Usually UL V-0 or 5V rated.

...sorry, didn't mean to hijack the thread, just want everyone to know that a fuse doesn't mean things won't get hot. They are very important, however, as most failures are shorts that draw a large amount of current.

broncoluv...maybe an issue with the switched power? Maybe the power is still on to the MSD box, and the distributor stopped at a spot where the ground is connected, drawing current?

 

[broncoluv]

No, my ignition is on a switch under the dash, and it was the first thing i checked, it was off. It had sat for at least four days,without starting. I have killed the battery in one night if i leave the key or the ignition on.

 

[Steve83]

Those numbers seem pretty random. It would take a really special problem to give a connector 0.5 Ohms, and have that be stable long enough to melt the plastic. If the resistance got THAT high, it would probably keep going as the terminals got hot, until they burned apart (infinite resistance).

But assuming it was stable somehow... for it to only pull 10A@0.5Ohms on a ~12-14V truck, it would have to be in a circuit that normally pulled 14.4-18.6A, so the terminal would already be sized to handle that kind of load without getting hot enough to melt.

I'm not saying it CAN'T happen (obviously it can), but it's not easy.

And in any case - the point is that EVERY circuit should be fused, and a properly-sized fuse PROBABLY would have prevented this thread.


BTW
I measured my truck's ignition circuit, which has a factory 20A fuse. It pulls ~2.7A running (any RPM) and ~1.1A KOEO. IDK why Ford put such a big fuse on it - it would run with a 3A.

 

[bmc69]

. I am done with msd.

Welcome to that club.

%)

 

[Jdgephar]

Steve83,

If you are ever in MI, I'll have to show you our board of overheated connectors and terminal failures in our forced failure lab. High resistance connectors due to corrosion over time have lead to numerous recalls in the automotive and appliance world. There's an IEC standard test for this in Europe, and A UL test for the US. The point is that you get a high resistance on a connector on a circuit that draws current above 15 watts. A poor connection will start heating. Crimped connectors are the worst, especially the pre insulated kind.