66F100

Hello and thanks in advance for your help, I'm totally puzzled because my 1966 F100 with what I believe is a 79 302 is burning up on me.

Last night it started and I let it run for about 20 minutes shut it down and when I went to start it back up it had trouble starting but got going after I pulled the choke and pumped the gas.

When I turned the key it wouldn't shut off even when I pulled the key out. When I looked under the hood the solenoid was smoking and the battery positive and starter/relay wires were melted and burning hot. The nut on the starter/relay side of the solenoid was actually glowing orange.

It wasn't until I disconnected the battery that it shut off.

Today I replaced the two cables and when I connected the battery terminals the truck started on it's own with the key in my pocket. Immedietly it melted the starter/relay cable and the solenoid was red hot again.

Is this my starter, ignition? Any ideas?

Thanks again, cheers!

R.S.LOGAN

Not an auto electrician , but you may have a few problems linked to fault .May be ignition switch and starter as suggested , need to get tested . A sticking switch could have damaged starter motor if it kept feeding live supply .The other thing worth checking is the earth / ground cable from engine / gearbox to body for security and clean contact . Best I can suggest to help you .

66F100

Thanks I checked the main ground last night and had replaced it about 2 months ago it clean and has good contact.

These might be silly questions but:

How do I test the ignition and starter?

If I need to replace the starter or ignition should they be matched to the 66 truck or the 79 engine?

Should the starter motor have a ground? I couldn't find one. Are they case grounded?

Thanks

R.S.LOGAN

The earth / ground strap I'm referring to is not the main one at battery , just in case that is the one you checked .There should be an additional one fitted .The starter usually earths through engine .Starter can be bench tested .Many years ago I had a car where the choke cable acted as an earth as it passed through bulkhead due to broken body / engine earth cable .It went red hot and smoked on cranking engine .Cant help you on other questions , but sure some members will be able to help and advise you when they come on forum later .

66F100

Thanks again. I suspect the starter itself is ok because the truck will start it just gets red hot, melts the wires and of course it strts without the key as soon as I connect the battery and it won't shut off until I disconnect or it melts through the wires.

I'm going to replace the ignition switch and see if that solves my problem but will also check the starter ground strap.

There is defintaley power surging through when I connect the battery but I think that is because the starter is staying cranked.

thefonz

Solenoid may be fried, I would disconnect the wore coming off the solenoid to the starter. Hook up the battery, if things don't go red hot on you, then you have isolated the wire or starter. If it still gets hot, then you know it is from the solenoid back. Just an FYI,(since I don't know what your knowledge is) There is a big difference between the ignition switch and the ignition lock. A lot of people consider the lock the switch.

66F100

Thanks I will try taking off the solenoid to starter wire first. It's the wire that gets really hot really fast and smokes at the solenoid. The solenoid was new not long ago but it could definately be fried.

I picked up the switch today and will try replacing it today. It is the switch and not the lock that I'm replacing.

66F100

I should probably replace the solenoid again anyway because that excessive heat probably fuse the internal contacts together... Maybe that's why the starter doesn't stop now?

66F100

Problem Solved!
Bad Solenoid Ground Shorted and Fused the Solenoid Sending Constant Power to the Starter

Solution:
Replaced all Battery and Solenoid Cables and Connections, Replaced Solenoid, Sanded and Cleaned Solenoid Ground Connection (in my case the passenger side fender wall)

Thanks For Everyones Help!

R.S.LOGAN

Good to hear you got it fixed , thanks for update .