Ok guys I have an interesting issue. While I'm driving, my truck will randomly shut off. Just like you turned the key off, it will die. Sometimes it will restart immediately, other times I need to get out, pull the wire off the coil, stick a pen into the barrel connector to widen it out, then pound it back on and the truck will start and drive away fine. Today when it did this (its a VERY random issue...not weather dependent), when I pulled off my BRAND NEW coil wire, the end is all blue. Like dark burnt blue. The truck was emitting a "burning" smell just before dying. I have tried 3 coils so far to try to remedy this (1 BWD chep replacement, 2 older OEM coils). They all cut out. So 2 questions:

Why does the truck keep doing this? All iginition components (ICM, plugs, wires, cap, rotor, coil, distributor) are pretty much new.

Why does it smell like its burning when it dies?

The issue does at least appear to be coil/wire related, since pulling off the wire, widening out the barrel and pounding the wire back on the coil seem to temporarily remedy the issue....

 

I should add that this thing "eats" coil wires like they're gas. It's as if it burns them internally and breaks the connections at the ends or something. This issue started back in December and I figured it was just because of an old wire. But now it does this almost every other time I drive it. Most times, when I'm stuck in traffic! Oh yeas and the engine is my 351M.

 

It sounds like you might not have a resistor wire in the ignition circuit. If it's straight 12 volts, you'll fry the coil. Have you checked?

The check - with the key in RUN, you should have ~ 6.5 - 8 VDC at the + side of the coil. If you have 12....time for a ballast resistor or to replace the resistor wire.

Your grounds are ok?

You could also try and get a 12 VDC coil if you don't have/don't want to replace the resistor stuff.

 

Why do you think the coil is related? Why is this thread called "overheating coil?" For all you know, the act of shutting off the engine and letting something else cool off is what solves the issue. This whole nonsense about physically altering the coil connector sounds like a giant red herring.

Assuming you're talking about the high-voltage coil wire (secondary side), that's not related to the resistor (primary side). If the high-voltage coil wire is getting discolored, it may not be seated properly. There is very little current on the secondary side.

A lot of folks immediately point to the coil because it's easily accessible and cheap to replace. When folks want something to be the problem, they think it's the problem. Forget everything you're thinking at this point and start over. When the truck shuts off, does it immediately restart? If not, do you have spark?

 

Sorry Im typing this stuff real quickly at work. When it shuts off, sometimes it restarts as soon as you turn the key. However, MOST times, it will NOT restart (it keeps cranking and cranking). When the latter scenario happens, no there is no spark.

 

The next time there's no spark, turn the key to RUN and measure the voltage across the battery posts, and then from the positive terminal of the coil to ground (with the coil connected). The coil voltage should be half that of the battery voltage.

 

Just because I am trying to recitfy this issue ASAP (its my DD), can I pull the coil wire off to simulate the no spark and then run that test? Stupid question, I know.

 

I also ask because as I said this issue decides to present itself at the worst available times...such as (but not limited to) stopping at a red light, cruising down the road at 45 mph on my way to work, sitting in traffic, etc. Litterally always the worst possible times if ya know what I mean.

 

You may have to drive around the block for a few hours after work...

 

Sure now ya tell me. Lol.

I got it home just fine...no stutters or anything. Didn't even cut out. I'll try fmc's test and report back with #'s.

 

Ok with no spark and the key in RUN, the measurements are:

Battery: 12.57 volts

+ Coil to ground: 4.50 volts

 

Did you do the test this way? Cuz if you did....uh oh.
🏃

 

Well ****...I did. Sorry I know I should have waited for it to do it again but I really have no idea if it will do it again in 10 minutes or 100 miles. Its really that sporadic.

 

FMC400 is gonna kick your....

Imma go hangout in another thread before he gets back, lol.

 

Yes, of course, you want to take the measurement during the failure condition.

Anyway, 4.5 volts is too low, spark or not. Are you sure you have the correct coil and not a "hot" performance coil? A "hot" coil will have too low of primary resistance, pulling the coil voltage closer to ground. The excess primary current through the ignition module causes heat-related premature failure.