I bought a 77 f150 351m. It was wrecked very light in the Rt front. When I bought it, it would not start. WE put a used starter solenoid on it and drove it home. I replaced fender and hood in the back yard and it would not stard. I taped the starter solenoid it started and ran for 15 min or so. I started it about 5 more times no problem. Started it up and noticed the starter solenoid smokin that was the end of that solenoid. I put another used solenoid on it started it up to bleed brakes, drove it over the hill and started back up the hill and the truck died. I thought it was out of gas. Today I put gas in it cranked it up and before I could get out of the truck it melted the + side of the solenoid. All my wires are ok no bare places or anything like that. Any ideas would be a great help. Is it posable the starter could be bad?

 

A bad starter can draw too much current and burn out the solenoid.

 

Yep. A bad starter will do this. Also bad wires from the bat to the sol and the sol to the starter can be the culprit too. Swap your cables to 2ga that will eliminate that issue.

 

Seems weird to meltdown AFTER the engine started.

Is the ignition switch sticking in START?

A heavily corroded cable and a failing starter can draw the solenoid down tremendously. Check the starter cable and if possible remove and have the starter tested.

Josh

 

OK now Iam about to take this truck to the scrap yard!!!! Not really I could never do that. I put a new starter on today truck started right up and again the solenoid started smoking.I quickly took the postive cable off the battery and drove it to the top of the hill. I double checked all my grounds again and checked to see if I could find any bare wires. Everything was good. I thought what the hay started it up and sat there and ran for 15min with my hand on the solenoid no smoke no heat everything fine. I turned the truck off for a min or less hit the key to start it one more time and the smoke rolled Iam at a lost,I think I'am going to replace the ignition switch and see what that does. Anymore ideas? I had the alternator checked out it is good.

 

Once again. Swap your cables with 2ga from the battery to the solinoid and the solinoid to the starter. I'd bet you a $100.00 that you have bad cables.

 

I agree with co425, replace your battery cables (including the negative).

If water gets inside of them, they can corrode (turn green) internally but you'll never see it.

Also ensure the ground is good from the battery to the block.

A replacement ignition switch is a waste of money, the only thing it does is feed power to the red/blue-stripe wire attached to the solenoid (#5 in the picture), this causes the electromagnet in the solenoid to bridge the two fat connections.



From Franklin2's diagrams:


Your problem is too much current being drawn through too thin of electrical conductors.

Either it's the cable connections, the cables themselves, the solenoid, or the starter.

 

OK Ill buy new cables today and install them.

 

I had similar issues, but my symptoms where a little different than yours. About every 4th time I started the truck, the engine would start and the starter would stay engaged.

In my case, I had a starter that worked but pulled WAY too much current and fried three different relays. I took one apart and you could see the pitting on the contacts. It'd fuse, I'd whack it with a hammer and that'd break the contacts free. Problem is that once you've done it a couple of times, now you have relay contacts that lose surface area and easily overheat.

I had to replace both the starter AND the relay at the same time.

Do what the other guys said to do (they are smarter than me), but if you've got a starter misbehaving, switch out both the starter and the relay.

 

+1 on the starter and solinoid at the same time. The solenoids only 8 bucks.

 

2 gauge is probably overkill for the cables. A new set of 6 gauge will work fine. Also make sure the solenoid is getting a good ground to the inner fenderwell. A bad ground will cause problems as well.

 

Have you checked it with a multi meter for a short ?

 

Yes, the contacts burn up and weld together:

 

Do what you want but I do not think 6ga is adequate. It may be on paper but go ahead and fry that puppy when it's hot as hell. Personally I like the extra insurance.

 

i am having the same problem i have tried everything but the new cables i am on my way to the parts store now to get all new 2 gauge wire please let me know what it was if you have figured it out if not i will let you know how the wires work.