Can someone help diagnose a weird issue that happened to me today?

[La Zona Imagery]

I was driving my truck today for about 10 minutes when all of a sudden, the tach started stuttering. The engine felt like the truck was running out of gas (i had a full tank). Then all of a sudden the engine died, and smoke started coming out from under the dash. I was able to restart the engine, and pull over to the curb. Ten seconds later, after the restart, the engine died again.

I opened the hood, but nothing seemed to be out of place. No smoke either in the engine compartment or inside the cab. I waited for about 10 minutes, restarted the engine, and everything worked fine again. I was able to drive back home with no issues.

Any ideas on what might have happened? The only thin out of the ordinary was right before it smoked, I drove over a rail crossing a bit too fast, and the lower a-arms might have slightly scrapped. But I do not see how that could have cause the engine to die or the smoke to occur.

[La Zona Imagery]

The white smoke seemed to be originating from underneath the center part of the dash. And it did not have any strong smell. I looked under there, but I do not see any obvious burned areas.

[ray_mcavoy]

A couple possible scenarios come to mind:

(1) There is a wire somewhere under the dash that is rubbing/chafing and intermittently shorting to ground. Going over the rail crossing could have shifted the wire enough to cause it to short out, killing power to the ignition, and getting hot enough to cause the insulation to smoke. From the factory, the main feed wire in these trucks is completely unprotected by a fuse or fusible link. So it would be possible for a momentary short in that wire (or one of the other unfused circuits) to cause something like this. Adding a fusible link to the main feed wire near the battery (like GM did in the 67 & newer trucks) is a good idea to prevent this type of thing from happening.

(2) Does your truck have a factory gauge cluster with a battery gauge? Those gauges are an external shunt type ammeter. Normally, the majority of the current flows through the heavy gauge wire that serves as the shunt and only a small fraction of the current flows through the meter movement itself. However, if there is a poor connection at either end of the shunt (red wire that runs from the positive battery post to the horn relay), it leaves the meter movement (and it's connecting wires) as the only path for current to flow through. And the 64-66 battery gauge wires (black & black with white stripe) are not protected by fuses so they (and the meter movement) will get hot enough to smoke if this happens. I've seen a few of these gauges & wiring burned up from that happening so I always recommend adding a couple of 4 amp inline fuses to those battery gauge wires (just like GM did in the 67 & newer trucks).

[La Zona Imagery]

Originally Posted by ray_mcavoy

A couple possible scenarios come to mind:

(1) There is a wire somewhere under the dash that is rubbing/chafing and intermittently shorting to ground. Going over the rail crossing could have shifted the wire enough to cause it to short out, killing power to the ignition, and getting hot enough to cause the insulation to smoke. From the factory, the main feed wire in these trucks is completely unprotected by a fuse or fusible link. So it would be possible for a momentary short in that wire (or one of the other unfused circuits) to cause something like this. Adding a fusible link to the main feed wire near the battery (like GM did in the 67 & newer trucks) is a good idea to prevent this type of thing from happening.

(2) Does your truck have a factory gauge cluster with a battery gauge? Those gauges are an external shunt type ammeter. Normally, the majority of the current flows through the heavy gauge wire that serves as the shunt and only a small fraction of the current flows through the meter movement itself. However, if there is a poor connection at either end of the shunt (red wire that runs from the positive battery post to the horn relay), it leaves the meter movement (and it's connecting wires) as the only path for current to flow through. And the 64-66 battery gauge wires (black & black with white stripe) are not protected by fuses so they (and the meter movement) will get hot enough to smoke if this happens. I've seen a few of these gauges & wiring burned up from that happening so I always recommend adding a couple of 4 amp inline fuses to those battery gauge wires (just like GM did in the 67 & newer trucks).

Thanks for the help. I think one of these scenarious might be the issue. I will check tomorrow.

[Metalaroundstone]

Originally Posted by ray_mcavoy

A couple possible scenarios come to mind:

(1) There is a wire somewhere under the dash that is rubbing/chafing and intermittently shorting to ground. Going over the rail crossing could have shifted the wire enough to cause it to short out, killing power to the ignition, and getting hot enough to cause the insulation to smoke. From the factory, the main feed wire in these trucks is completely unprotected by a fuse or fusible link. So it would be possible for a momentary short in that wire (or one of the other unfused circuits) to cause something like this. Adding a fusible link to the main feed wire near the battery (like GM did in the 67 & newer trucks) is a good idea to prevent this type of thing from happening.

(2) Does your truck have a factory gauge cluster with a battery gauge? Those gauges are an external shunt type ammeter. Normally, the majority of the current flows through the heavy gauge wire that serves as the shunt and only a small fraction of the current flows through the meter movement itself. However, if there is a poor connection at either end of the shunt (red wire that runs from the positive battery post to the horn relay), it leaves the meter movement (and it's connecting wires) as the only path for current to flow through. And the 64-66 battery gauge wires (black & black with white stripe) are not protected by fuses so they (and the meter movement) will get hot enough to smoke if this happens. I've seen a few of these gauges & wiring burned up from that happening so I always recommend adding a couple of 4 amp inline fuses to those battery gauge wires (just like GM did in the 67 & newer trucks).

I also have the original ammeter in my truck. Would you mind providing more detail on how to wire the couple of 4 amp fuses? It sounds like something I should also do to AVOID smoke under the dash. Thanks

[ray_mcavoy]

Originally Posted by Metalaroundstone

I also have the original ammeter in my truck. Would you mind providing more detail on how to wire the couple of 4 amp fuses? It sounds like something I should also do to AVOID smoke under the dash. Thanks

For 1964 through 1966 Chevy, the battery side of the ammeter is connected to the large BATT stud on the starter solenoid with a black wire (about 18 or 20 gauge if I remember correctly). That wire runs inside the engine harness until it reaches the 6-cavity bulkhead connector plug on the firewall (just above & off to the passenger side of the engine). You'll want to place one of the 4 amp inline fuses in this black wire. The ideal location would be down near the starter solenoid (to protect the entire length of the wire). But it isn't always easy to place a fuse holder down there so you might have to place it farther up the wire (closer to the firewall plug). That location will still provide protection to the meter and the wire inside the cab.

The alternator side of the ammeter is connected to the 2-screw terminal buss bar that is part of the factory horn relay. There will be several larger (12 gauge or so) wires connected to these terminals along with one smaller (18 or 20 gauge) black wire with a white stripe that goes to the ammeter. You'll want to place the other 4 amp inline fuse in this black wire with the white stripe. Locate the fuse on the end of the wire close to the horn relay.

If you're going for an OEM factory look, you could salvage some fuse holders out of a 67 to 72 (or even 73 to 75) GM truck with an ammeter. But for functionality, most any inline fuse holder will work. They type that have rubber caps on them to keep out moisture & dirt are a good choice for in the engine compartment.


The 1963 ammeter setup is very similar to 64-66 described above except for the color code of the wire connecting the ammeter to the buss bar on the horn relay. It's red instead of black with a white stripe.

The 1961 & 1962 trucks originally had generators (instead of alternators) so they use the "B" terminal on the voltage regulator (instead of a buss bar on the horn relay) as the main power distribution point. The ammeter still ties into this point with a small red wire though (and this is the wire where you'd add the fuse). And according to the factory wiring diagrams, these years (61 & 62) did have a 3 amp inline fuse protecting the black wire that goes to the starter solenoid BATT terminal. I'm not sure why they eliminated that fuse for 63-66.

I don't have much info on the factory ammeters used in 1960. I think they might be the same as 61 & 62. But there is a possibility that they were the full-flow type (not external shunt) where all of the current goes through the meter movement. That type would be easy to recognize by the fairly heavy gauge wiring (probably around 12 gauge or so). That design would have to be protected with much larger fuses (or fusible links) instead of the small 3 or 4 amp fuses that can be used with the external shunt style meters.

[X24]

a while back i had a similar issue minus the smoke... truck would run a couple minutes and stall. the start back up and run for a minute and stall eventually it was 30 seconds and die..... took a while to figure out it was spark... distributor issue... $11 condenser wire. boom done finished.
of course it cost me $300 to pay someone smarter than me to fix it.
worht every penny.