Starter Won't Disengage (95% of the time)

I'm confused!  So far I have replaced....

Starter
Solenoid (lifetime AutoZone)
Ignition switch
Battery cables/starter cable
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Lubed up linkage to ignition switch
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In the summer the started got stuck engaged and melted all the wires and even had melted the positive battery terminal it was glowing red in the bright sun lol.
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I have been messing with my truck today, I miss driving this beast, it's been out of commission for a couple months.  It's a 1986 F150 4.9 I6, Duraspark II converted, cheap $60 eBay carb.  Been going hard and strong with pretty much no major issues for almost 2.5 years until this started happening.

Today I replaced the ignition switch and lubed up the super sticky linkage.  Hoping the issue was a sticking ignition switch.  Starter the truck fine just using a screwdriver in the ignition switch (not mounted), truck started fine.  Cool I was able to move my truck for the first time in months. So, I then put the ignition switch back on the steering wheel shaft.  Tried to start the truck again, starter got stuck engaged again wtf!  Took ignition switch back off tried to start with screwdriver again, starter is stuck again!

If I take the little red wire off the solenoid, it is still cranking. The only way to stop it is to pull the negative cable.

Could the DuraSpark II module itself be messing up?  Try another solenoid???  Everything is new!  How is this happening?  

Thank you in advance for your help.

If you remove the little Red/Blue trigger wire from the starter relay and it continues to crank, the relay has welded itself closed.

Try hitting the relay with a screwdriver handle or something similar before disconnecting the battery ground.
Often just jarring the relay coil is enough to make the contacts disconnect.

Test the red/blue wire with a test light or buzzing DVOM. So you can work the key with the ignition switch installed and still know that the (S) trigger wire is acting as it should.

Our friend Chris Tubutis dissected one of these starter relays over on FTE (where he was moderator) and showed that the contacts were simple iron rather than solid copper or even silver plated.

So, even though you've replaced everything.... It may be down to a poor relay or there may be a resistance in the circuit that is causing the relay to have to pass too much current.
If the battery ground cable, starter cable, positive to relay cable are all solid clean and tight I'd be looking at doing a voltage drop test across each and using an inductive pickup on the starter to see how much it is really drawing.

Quality fender relays can be found through upfitters or dedicated automotive electric sellers

There is a reason people change to a PMR starter, it does away with that relay. It costs a bit for a new starter and there is some wiring to do, but all reports I have read are food.

I have had many relays fail. I only use motorcraft ones now and they seem really reliable.

Well, Ford's implementation of the PMGR starter didn't do away with the fender mounted relay.
It just used it to trigger the solenoid on the starter. (Which Gary recently reminded me was 44A to pull, and 14A to hold)

The thing I see that differentiates the Motorcraft relays is that they all having diode suppression.
.... although they don't seem to be listed as having copper contacts.    

https://www.texasindustrialelectric.com/relays.asp
See 15-436 & 15-450 for 3 & 4 terminal fender relays.

Im gonna get a new solenoid tomorrow at AutoZone. I'm gonna upgrade to the motorcraft when I get some extra funds and just keep the lifetime AutoZone one as a backup in the glovebox.

I smacked the solenoid with the socket wrench it it stopped :)

Jim is right on how the PMR starter is wired and my drag car is wired the same way with out any issues.

Newusr wrote

Im gonna get a new solenoid tomorrow at AutoZone. I'm gonna upgrade to the motorcraft when I get some extra funds and just keep the lifetime AutoZone one as a backup in the glovebox.

I smacked the solenoid with the socket wrench it it stopped :)

You like so many other go for the cheap solenoid and it comes back to bite you.
I knew of this issue and when mine started acting up, would only get a "clunk" from it a few times before it would start.
All my cables were new from rebuilding the truck and not even 2 years old. I also cleaned all connections again before I replaced the solenoid.

I replaced it with top of the line NAPA solenoid and have not had any issues since.
BTW the solenoid needs to have a good ground to the inner fender.
Dave ----

So the solenoid actually grounds itself where it touches the fender?


I got it going yesterday with my warranty exchange.

Yes they ground through the two little mounting screws

i will second the decision to only use motorcraft starter relays from now on. too many failures with store brand ones. when i have to warranty "my" work , it no longer matters that i saved the customer 20 dollars on the part. im starting to keep more motorcraft on the shelf even though i need to order them most of the time. i recently had this exact thing happen and i had to handle it. it was since i had moved but i was back in town on other business so i brought a motorcraft relay and handled it in the feild. with a smile!

That is great customer service! I need a guy like you near me!