I have an 86 f-150 351 HO that recently started having starting problems. When trying to start the engine it will crank and crank and not start until you let off the switch then it will start. I figure it is time for a new starter solenoid. The solenoid that I had on it for years was an earlier model like from the sixties or seventies and has worked fine up till now. So I go to Napa and get a new Echlin solenoid switch that is for an 86 which is the big round one like came with the truck new. I hooked it up and when I tried to start it, it just kept cranking over even when I shut the key off. I jumped out and loosened the battery cable from the battery and pulled it off to stop the engine from cranking. Mind you the key is off, so I touched the battery with the cable and it takes off cranking again. It didn't do this when I first put the solenoid on until I tried starting it with the key. Now it spins over with the key removed from the switch.
This new switch has 2 small posts on it, one marked "s" and one marked "i". I hooked up the small wire to the "s" just like the older solenoid. I hooked it up according to the instructions. I had problems with this years ago so that's why I put the older type solenoid on it and haven't had any problems for years. Has anyone had this problem? I'm out twenty-five bucks 'cause I can't take the solenoid back. HELP! Bud

 

Hey Bud,
have you searched the site and or google for anything? I remember when I was having starter problems (physical gear/flywheel issues) I remember coming across some sticking starter threads. Same situation you're having. As to why this happens I can't remember...but sounds like a solenoid issue to me. Sucks youre out the cash but can you use your old one at all?

Solenoids are very simple. You have two smaller, low power terminals that are used to activate a high power switch. The other two terminals are the high power switch input and output. It's kind of hard to mess it up. I mean you would pretty much have to try by replaceing the ring terminals at the ends of your wires so they fit on the opposite terminals.

One of the small terminals is connected to the coil ground. The second small terminal gets a + power from the key switch when you turn the key to crank. Simultaneous, the coil activates and pulls in a high power switch connecting the battery side power feed to the starter motor. Sometimes other items may be tapped off the battery side but you would know if that was backwards because you'd only have power to a device when you switch the key to start.

So going back to your issue...it sounds like one of two things. You (or the solenoid you have) have a stuck solenoid or a stuck ignition switch (not the key, the physical switch under the dash). How good are you with volt meters and such? Simple diagnosis to start: take the large wires off the solenoid (these are the battery and starter motor cables). Make sure the battery side does not touch anything grounded (not that you wouldn't but my dumba$$ would easily for get this until the 4th of july arrived early LOL). With the key off, your volt meter on 12volts or whatever scale that's higher than 12v and the batter reconnected, meter the two small terminals. If you can find which side is the ground put that on the black terminal of the meter. If you have 12v or 11.8 or 11.2 or anything above 0.034 (sometimes the meter picks up stray voltage) you know the switch is stuck and providing power to the solenoid. If you have nothing you most likely have a stuck solenoid....

Simple start. Let us know.

 

The not starting until you let off of the key sounds like a bad ignition module. There are 2 ign curves built into it. While cranking the module retards the timing to make it crank easier. The retard mode in the module is probably burnt out.

 

There's another probability on not starting until you let off the key. The issue comes from the fact that there are two sources of power to the ignition system - one in the Start position and the other in Run. Sounds like you don't have power in the Start mode to the ignition system but do in Run.

If you do have a volt meter then check the following:

• At the ignition module: White/Light blue wire is Run, and you obviously have power there in the Run position
• At the ignition module: Red/Light blue is Start, so check that you have juice there when the key is in Start. You can pull the little wire to the solenoid to prevent the engine from cranking.
• At the coil: Red/Light green should have something less than 12v in Run since there is a resistor in the line for Run, but full 12v for Start.

It is likely that the ignition switch is actually bad and is not supplying juice to either the coil or ignition module in Start but is in Run. And, it takes two to tango.

 

Did you try using jumper cables?

A bad battery will also cause the engine to start after the key is moved from the start to ON. The battery voltage jumps back up after the starter disengages, the higher voltage to the coil now is enough to provide spark at the plugs, as the engine is still spinning.
Have you checked your spark plug gap, it might be larger then it should be.
Jim

 

Does the engine stop cranking if you take off the "s" wire? That one small wire is what is responsible for activating the solenoid.

Im gunna go with Gary on this one and say you have a faulty ignition switch.

 

Sounds like good advice. If you don't have a meter just try the spare module you most likely have under the seat.

 

After reading back through this thread, it seems that he has two problems. The one most are addressing is that the engine does not actually start until after the key is released from "start" and returns to the "run" position.

The "other" problem is the fact that after replacing the truck's starter relay with a good name brand aftermarket one, the starter motor continues to spin even with the key removed. Sometimes, even new replacement parts are "bad" out of the box. Once the relay was used for the first time, the contacts might have "welded" together and then not released.

 

The new solenoid is welded internally.
Try smacking it the next time it gets stuck on, instead of removing the battery cable.

Try connecting the 'I' terminal of the solenoid to the white wire of the DSII module.
That's how they were wired back in the '70's
If that doesn't work, then you can assume the coil isn't getting juice from the starter bypass splice, and could connect the 'I' terminal into the ignition harness to provide 12V while cranking.
The DuraSpark system provides 12V to the coil while cranking, for a hotter spark, and ~7V in 'run' to keep the coil from overheating.

 

Thanks to all that responded to my HELP situation. I have just about replaced everything that was suggested from all of you including the starting solenoid, ignition switch, and Module, which I did have a spare Blue Grommet Module.
I haven't got it together yet but am confident that all your help will have it going tomorrow. Had to quit for today because of company coming to dinner.
Thanks again guys and Thanks Jim for the wiring schematic, I copied it and enlarged it for a keeper! Bud in AZ