I recently inherited a 79 ford f150 with a 302 from my father in law. He had been storing it for about 12 years for a friend of his, and finally decided to give it away. He spent a few weeks and several hundred dollars fixing a few necessary things, including a new battery. After driving it home, I could no longer start it. I cranked the engine and pumped the gas trying to get it started, and stopped when I noticed smoke coming out from under the hood. The cable from the positive battery terminal to the starter relay was melting the insulation off. I bought a new cable and tried to get it started again. I realized it was some problem with the gas flow. I had my wife crank the engine after I pulled the fuel line off to see if any gas was getting through, only to find that it wasn't. The point is she left the key in the "on" position, and after returning to the truck about 15 minutes later, I found billowing smoke pouring up through my heater vents and speaker grill in my dash. After disconnecting the battery, I felt the ignition wires in the cab, and they were hot. I have limited knowledge about vehicle electrical systems, and I'm not looking forward to pulling out the instrument cluster to get to these wires, and then having to replace them. My question is what went wrong? Could it be the wrong battery? Is it just a shorted out wire? I don't want to replace the wiring and have it happen again. Any advice would be appreciated...

 

Battery won't be your problem. Did the positive cable melt again or is it okay? Sounds like your relay/solenoid has something shorted out in there but I'm not sure why you'd be experiencing smoke from under the dash. Do all your fuses look okay or are they burned?

 

Actually, the new positive battery cable that I put on there is fine, and none of my fuses blew either. I still haven't had the chance to take the dash apart to get a better look, and when I looked under the dash with a flashlight I didn't see any wires with melted insulation. There were a few electrical quirks that I noticed before it stopped running. When I would go over a rough bump the radio would make a sharp cracking noise out of the speakers, and the right turn signal arrow light in the dash didn't work even though it looked like the bulb was still good. The cigarette lighter also didn't work. I don't know if any of this has anything to do with the smoke though. Could it just be a bad ground connection?

 

After reviewing my Haynes manual's section on the electrical system, I found this quote: "Never leave the ignition switch on for long periods of time with the engine not running." It doesn't give any reason not to do this, but maybe thats all my problem was. Maybe there was no electrical problem before, although with all of that smoke I'm sure there's one now Does anyone know why I shouldn't leave the switch in the "on" position for any length of time?

 

What page is that on ?

 

"Haynes Ford Pick-ups and Bronco 1973-1979" page 5-2, under general information.

 

Leaving the ignition on for long periods can overheat the ignition coil and ruin it.

If you found nothing wrong under the dash, the smoke could be from the heater fan speed resistor. If a leaf or old mouse nest gets up against the resistor, it will start smoking, since the resistor gets red hot when the fan is on low.

There is a possibility your battery cable overheated from cranking the engine too long. While you are troubleshooting your fuel problem, go easy on the starter. Crank it for about 10 seconds, and then let it rest a minute or so.

An easy way to see if you have gas is to take the aircleaner off, and while looking down the carb throat, push back the throttle linkage. You should see two strong streams of gas.

I am sorry to say, but more than likely you will need to clean the fuel tank out, put a new fuel pump on, and rebuild the carb. The fuel has gotten old and stale, and is probably sludge in the tank, and I have seen it ruin fuel pumps and rot out the gaskets and diaphrams in the carb. This is the price for letting it sit so long.

 

Hey tooldude, Franklin made some good points about your fuel system, but I'm real interested in the electrical problem. Wouldn't it be just an accessory or associated wiring at fault with the key left in the "on" position? Was the smoke mostly at the top of the dashboard or coming up from the bottom? Middle or what side?Smell like wiring or plastic etc...? Do you have power to any accessories (radio, lighter, dash lights...)?

 

I should clear up the fact that I found the fuel problem. Once I realized the (new) fuel pump wasn't pumping any gas, I dropped the fuel tank and looked inside to find a ton of crystallized rust on both the tank and the fuel send unit. I've already ordered both of the necessary parts to replace them.

To be honest I haven't hooked up the battery since the smoke incident, but I'm sure my dome light was working when I disconnected it. The smoke itself was coming up through the defrost vents and the speaker grill located in the center of the dash. The smoke stunk like melting plastic, and maybe burning dust. I would really like to find out if this is a one time thing, or if this is something that will happen again...I appreciate all of the advice

 

Ok, so I've taken the dash apart and found the problem. One of the wires going to the key ignition pretty much melted. It was red with a green stripe, and has the words "resistor do not cut or splice" printed on it. It also had some type of extra woven insulation over part of it. I took all of the tape off the wiring bundles and followed the wire down to one of those black rubber things that look like fusible links. There I found that a thinner brown wire was also connected to the same link. On the engine side of the link, the wire is orange and red. What exactly are those black link things? How do I replace one? I've noticed in other places that the words "fusible link" are stamped on them, but there are no words on this one. It just looks like something that is used to connect two wires to one.
Many of the other wires in the bundle have bits of the melted wire on them, and they were stuck together, but I don't see any missing insulation on them, so I don't really want to replace them all.