Gentlemen, I would greatly appreciate your input. I am having a problem with my 85 F250 4X4 351W 4 speed manual transmission. The problem is random, no telling when it will happen. It may happen first start in the morning or after I have started it several times that day or after it's been started once or twice, just no telling when it will or even IF it will happen that day. I have detected absolutely no pattern to this problem.

So here's the problem. Randomly the starter solenoid will stick/lock in and no matter what you do in the cab it WILL NOT disengage. I can turn the key off and remove it and it is still spinning the starter. I can put the truck in neutral or in gear and let the clutch out and the starter keeps right on spinning the motor over. The motor will not start but the solenoid is locked in and the starter is spinning the engine like I'm turning the key trying to start it. To stop it I put the truck in neutral, pop the hood and hit the solenoid with my fist (ouch) or a hammer handle. Usually one hit will stop this, occasionally it takes two hits. It's been doing this for about a month now.

What I've done so far. I have replaced the solenoid, I'm on my 4th solenoid as of last Friday and I still have the problem. I have installed one mediocre solenoid and worked my way up to the the best quality solenoid available in my area. I have replaced the alternator and voltage regulator in case they were over charging my battery, also because my head lights were surging, this fixed that problem. I have added a ground wire from the solenoid mounting bolt to the battery ground terminal. My battery is an Optima battery. With the truck idling my volt meter is showing about 14.7 volts going in the battery, across the battery terminals.

This problem started out of the blue, I haven't changed anything on the truck in the last couple of years. I am scratching my head on this one, so far the solution has evaded me. I thank you for taking the time to read my thread and would appreciate any and all input that would/could help me solve this mystery. I am electronically challenged, LOL, so please try to respond on an elementary level.

 

 

You're not the first person to experience this. Try this thread:

https://www.ford-trucks.com/forums/1...solenoids.html

Six pages' worth of wailing and gnashing of teeth, and the final fix was a genuine Motorcraft relay.

 

If he is using the best he can get it may not be a cheap part as the cause.

Yes I would replace all the battery cables with new large ones.
Watch the parts stores as the also have thin ones.

Next time this happens pull the small wire off the solinoid on the "S" lug and see if this stops it.
If so replace the ignition switch down low on the column. If replacing that does not fix it you will need to find why that wire has power to it when key is off.
Dave - - - -

 

 

went thru this with my '68 ranger, tried solenoids, replaced starter, cables, was my ignition switch.

 

Thank you gentlemen I really appreciate your input helping me with this problem. I am going to replace the battery cable from the solenoid to the starter with a heavier one today. I will definitely try your suggestions IF this doesn't fix my problem and remove the wire from the S lug on the solenoid. I can do fairly well working on mechanical things but in all honesty when it comes to electrical issues I am basically a parts changer. In my feeble brain for some reason it seems logical to me that since I can hit the solenoid with a hammer handle and it stops, the solenoid is arcing and sticking, again this is my feeble brain thinking.

Thank you for the link kr98664 I did a search before I started this thread but didn't find that one.

Again I really appreciate your help, suggestions, and input gentlemen, thank you.

 

 

Thank you again gentlemen I appreciate your ideas and input.

kr98644 I read that entire thread and I appreciate the explanation you gave about the solenoid to starter cable as well as your other input. However I did go ahead and replace this cable since I've tried most everything else, looked like I was shoving a welding lead down to my starter LOL. I also cleaned all my ground connections again.....just in case. I will see if this made any difference. I've only started the truck 3 times since doing this without an issue but it'll take a week or so to know if it's fixed for sure.

Odisvan I agree, I don't know much at all about electronics but the one thing I have learned over the year messing with these older trucks is check the ground first. My wife and I bought a new fishing boat, motor, and trailer back in June. The trailer lights were all screwed up when I got home with it, bout an hour and a half drive. They sprayed the trailer with bed liner then wired it for the lights. Needless to say the ground for the lights was a mess. I removed the ground wire at the trailer tongue, cleaned off some bed liner, put the wire back in place and the lights work perfectly.

 

What brand starter relay is currently installed?

If you have a clipboard and a lab coat, my thoughts are you could be part of a ControlledScienticExperiment™. If so inclined, don't make any more changes until it either fails again or enough time elapses that you're satisfied it is fixed. That way, when the next guy posts about a starter relay sticking, we can direct him here and say XXX didn't help but YYY was a good fix. In other words, if you have the luxury of time, don't make a bunch of changes at once or we won't know the actual fix.

I find this all very interesting as the starter relay on my truck is probably 20 years old and has performed flawlessly. It was a NAPA Premium replacement, circa 1998. The battery cables are original, except for the short one from the battery (+) terminal to the starter relay. Why has my truck behaved while others are acting up? I'm still learning towards the quality of the starter relay, but have no way to prove it. If newer replacements aren't welding themselves closed, perhaps it's some sort of residual magnetism due to manufacturing shortcuts these days. All conjecture, really...

 

 

Wish I had one acting up in front of me so I could run some tests. I'd be curious about the findings of a voltage drop test on that suspect cable. That would fit with my previous theory (Squirrel!) of low voltage at the starter relay causing reduced clamping force on the big internal contacts. However, if that theory was correct, you'd expect to see arcing. At the thread linked above, that was definitely not the case. Failed relays were cut open and looked fine inside. That's why my TheoryDuJour™ involves residual magnetism. I'll be on to something else tomorrow...

I should mention my starter relay was replaced years ago for slow cranking. It failed a voltage drop test. The cable was replaced more recently as a precaution due to external corrosion at the battery end. It was still performing fine at the time.

I don't doubt you for a minute about your fix, and what seems like a fix (knock wood) here. I'd just like to figure out exactly why. So far nothing I've come up with fits the bill 100%. I must be overlooking something like sunspot activity or a shift in the Earth's magnetic core.

Do you have a link to the article you mentioned? Maybe that has some answers.

 

 

Well gentlemen the truck has been cranked 2 more time without issue. The solenoid I have on the truck is a motorcraft brand, but I don't have the part number in front of me. It's a 3 lug solenoid, 2 for the large cables and 1 for the control wire.
kr98664 I do have time for an experiment but I don't have the knowledge on how to conduct an electrical experiment. If you are willing to drive this wagon I'll be happy to help pull it. I would really like to know what is or was causing this problem. I was like you, ran the same set up (parts) for years. Same cables, same solenoid, same under dash starter switch, same battery, same alternator, same voltage regulator, same ignition set up (if that matters). Then out of the blue one day the solenoid locks in. No big deal I'll replace the solenoid. Just bought a cheapo from local parts house, it locked in too. Dang cheapos, that's what I get for buying a cheapo. So I bought the NAPA brand, it locked in too. Went back to NAPA and told them what it was doing, he sold me the best brand they had on the shelf, it locked in too. So I went to a parts house across town, Bumper to Bumper, (hope I can say that) and talked to a buddy of mine. He told me the best he could get was a motorcraft brand for about $35.00. I installed it and guess what......it locked down too. That's when I posted this thread. Now I have installer a bigger cable from the solenoid to the starter and we shall see. When it comes to electrical stuff the only thing I know is.....DON'T let the smoke out of the wires LOL. Again I thank you gentlemen for all your help and input.

Oh yea, I won't change anything else on the truck concerning this problem until it messes up again, especially since I don't have a clue what else to do. I'll report back as the days go by to give you updates on how its doing. Hopefully it's fixed but only time will tell.

 

At least we're not alone in the hunt. I hope this link works, I'm also computer challenged LOL.

https://www.stangnet.com/mustang-for...e-time.823909/