So I have been working on a third engine in my 79 Jimmy (long story as to why it's the third engine) and I've come across an issue.

I had gotten to the point of turning the engine over, and when doing so, it turned over very slowly. This was on an engine that had sat for quite some time, so it was to be somewhat expected. I pulled out the spark plugs, put a few squirts of lubricant into the cylinders, and cranked the engine over to lube things up.

The battery had started dying, so I hooked it to a charger, let it do it's thing, put the spark plugs back in and tried again. Now, the starter was not cranking. To save some time in the story, I ended up switching starters, and tried again with the same sound and same lack of spinning. The engine was free as I cranked it over by hand, so it wasn't locked. I assumed this was from a low voltage issue. I tried again and again unsuccessfully to crank the engine and finally gave up.

This is where it gets weird. I got out of the drivers seat, and immediately smelled smoke. It was almost the smell of electrical wires melting, so I initially looked everywhere under the hood. No smoke under the hood, no smell of it there, now was it in the cab. As I turned back towards the drivers door from the hood, the sun had caught the smoke so I could see it. I followed it all the way back to the driver side rear brake drum.

It was literally pouring white smoke out of the top half of the drum. And it only did this when I was attempting to turn the engine over. It has done it once or twice prior, but we never found it. And that was when the engine was spinning slowly.

This truck has been parked for going on 5 years now. Hasn't moved an inch in that time. So I ask, What could actually be causing this smoke? It is clearly from the drum, and only happens after a somewhat long session of cranking the engine over. There are no wires running in, over, or around the axle or drum.

 

There is no smoke coming from the brake drum if the truck isn't moving. Probably some wiring issues near that side of the truck where that brake drum is.

 

So then, what exactly is coming out of the brake drum that smells like burning plastic?

Care to give me an idea as to where to look for these wiring issues? There isn't much back there as it is. Tail lights, and an electric rear window. The trailer lights have been disconnected and removed.

 

That's the truth right there, great insight.



How long are you cranking the engine at one time? You can heat up the ignition wires and positive cable with prolonged cranking. Eventually this will melt the coating off the wires and then short out if they are touching anything on the frame. In the case of the positive wire there is no fuse so if it melts, shorts you could be looking at the end of your rig...

When cranking there is no power to anything other than the starting circuit. I don't see either how there could be smoke pouring out of the brake drum. I also don't understand how you could see the brake drum with the wheels on...

Was there any wind? could a little puff of smoke have been carried to the rear of the vehicle?

another question, when you say it cranks slow is it like a whir---whir---whir like the timing is too advanced? Does it crank the same with the plugs in or out?

 

The engine (when spinning) would get cranked for no longer than 15 seconds. If the engine is not spinning, then I try the ignition about 5 or 6 times, with maybe 3 seconds per try.

I'm currently trying to get the engine to run, so I can check timing. I've moved the distributor around when it was spinning and got nothing different when cranking.

I haven't yet taken the plugs back out to check if it makes a difference as that would have been my next move. The truck is currently at my parents house taking up space in their driveway.

As for seeing the smoke, I stuck my head inside the wheel well and saw it coming out the back of the drum. I'll be checking the wires when I get back to the truck as well.

And if it smokes out of the drum again, I'm certainly going to get pictures and video of it.

 

make sure your big positive cable is hooked up. i made the mistake of cranking the engine without it on and caused a bunch of smoke. other wise those little 10-12 gauge wires for your interior is trying to start the truck. also goes the same for the giant black ground wire off the battery

 

That's the truth right there, great insight.