I got my cab swapped over and it fired right up but it was too good to be true. I turned the key back and took it out. The truck continued to run also when the key is on the starter keeps turning. Does this sound like the ignition switch is shorting out? I have another switch that I can put in or should I try to rewrite something? Thanks

 

Could be the ignition switch, or the starter solenoid

 

Check out a similar thread in the 80-86 forum.

 

Bingo! 9 times outta 10 the ignition switch is the culprit...sometimes you can get away with just pulling it out and cleaning the contacts.

 

Cab swap sounds like some wiring would have been messed with or changed over. Am I right?

 

Ok well today was TERRIBLE. first off the truck would not crank. I broke out the multimeter and with the key in the run position the I post on the starter delay was receiving 7.5 volts and the S post was receiving .5 volts. When I turned the key, the S terminal was still receiving .5 volts. I pulled the ignition switch off of my 78 and then realized that it was the wrong size. So I went to my dads 77 and checked it out. It appeared to be the same. I decided that it would be a good idea to try use his ignition switch just to make sure it would work. I turned the key to acc and then inserted a piece of wire in and pulled the key out. I looked up and there was smoke rolling out of the hood. I disconnected the battery and it stopped. By this time I already had the ignition out so I took it to my truck and tried it out. Same results. So I put the ignition back in my dads truck and now there is nothing no headlights no radio. What could this be?????
Also what should I do about my truck I have really considered swapping the whole harness out of my 78 but it would be terribly hard.

 

I can't really follow anything you're saying. For example, I have no idea what this means:

A wire in what? The mailbox? Your pocket? I mentioned in my last post (which you did not address) that a cab swap sounds like a lot of wiring would have been messed with and changed out. Now you've suffered an electrical fire - it's anybody's guess as to what you're working with now. Your best bet is to start over with a junkyard harness, or at least inspect where the smoke was coming from. If you can't make it clear exactly what you're working with, no one can really help you. I should be able to replicate all of your steps to a tee on my own truck without having to ask you any questions.

 

You may not be familiar but when you pull the key bolt you turn it to acc (accessories) and then insert a piece of wire or paperclip then turn and pull the key bolt out.
As I said in my post. The fire was on my dads truck. A running driving 1977 f150. The fire was not involved with my swap. I have a 1977 f100 on a 1978 f150 frame. I was just borrowing the ignition switch because the ignition switch was different on my old 1978 f150.
QUESTION
It is my fault for not disconnecting the battery but what would cause a electrical fire from just removing the key bolt?

Also I am sorry I did not reply to your post. When I swapped the cab over nothing was cut or spliced of altered in any way. Everything plugged back in.

 

Could be a wire is getting pinched some place , easy to do when you are swapping cabs. I hate auto electrical , house electrical , no problem i can do that in my sleep.

 

Okay what probably happened in you're dads truck is when you pulled the ignition switch through the hole in the dash, then under it to unplug it it probably rubbed some wires together at the switch.. check you're fuses and that'll be why some of you're dads accessories aren't working.. if you're lucky it only got hot enough to smoke the wire under the hood.. you should DEFINATELY check the wiring under the hood though to be sure it didn't melt the insulation completely off any wires.. electrical problems are a huge PITA!!! Good luck, hope that helps..

With you're truck, did you keep the duraspark box on the driver fender well and all its wires with the original motor? I'v had bad luck a few times with mine getting wet and doing crazy things.. this is a pic of it..





but the starter continuously running is either corrosion in the starter or a bad ignition switch.. IMO The best way to eliminate the starter is to take it off the truck and bench test it

 

You could definately get it going with a electronic hei style distributor,



an ignition switch







and a starter button..

 

Thanks for all of the help. I sorted everything out on my truck. The wire that runs from the ignition switch to the S post on the starter relay was shorted out. I spliced it and ran a whole new wire. I am going to get back to my dads truck here in the next day or so. Thanks again for everything

 

A sticking starter solonoid will cause something very similar to this. Also can cause engine to continue running even after the switch is turned off and the key removed.

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I really think it was just the wire from the switch to the delay shorting out. First it wouldn't stop running, then it wouldn't start. After replacing the wire I haven't had any problems.

 

Glad you got it fixed
Any luck with you're dads truck?