Starter Will Not Disengage

I have a IH 2410B industrial tractor. The starter will not disengage with disconnecting the battery cable. I have checked the switch, replaced the solenoid, had the starter checked, replaced the wires from the solenoid to the switch and called it a bunch of names. Anyone have any ideas? It is a Delco starter. Thanks, Don

Pull the small wires off of the starter relay (that are connected to small terminals) if it still tries to start with the wire off, it is the relay. If that makes it stop trying, it is the switch (key or push button) Jim

It is a key type switch but I have it disconnected. I was just shorting out the wires to engage the starter. For like of a better term, hot wiring it. When you release the wires it just keeps on turning over.

She said it will not disenguage with the battery disconnected so removing the wires wont make any difference. She must have a bad bendix and or ring gear.

You might try holding your tongue right and then rapping on it with a BFHammer and see if it disengages.

OK. I am not explaining this very clear. When I try to start the tractor the starter just keeps running. In order to stop it I have to disconnect the power to the starter aka battery wire. I am not letting the tractor start up yet because there are a few other things I want to do to it before I let it start. I tried tapping on it and that did not help. I have never seen this problem before except a shorted wire against the frame. I have ruled that out. Surely there is someone out there that is smarter than I am.

if your starter solenoid actually pushes the bendix to engage it instead of the starter starter armature turning to engage it , the problem is more than likely the snap ring an collar that stop the travel of the bendix missing,broken or not locked in place causing the solenoid plunger to bottom out keeping the contacts engaged until battery cable is removed

That makes sense. Would this still happen if the starter is pulled off the tractor and left hooked up to power and enguage it. Would it still stay engauged?

It would nice if you had a volt meter connected to the S terminal on the solenoid and see if battery voltage is present when you separate those two wires. If there is voltage on that terminal, voltage is back feeding your solenoid. Hal

(quoted from post at 19:42:15 12/23/10) if your starter solenoid actually pushes the bendix to engage it instead of the starter starter armature turning to engage it , the problem is more than likely the snap ring an collar that stop the travel of the bendix missing,broken or not locked in place causing the solenoid plunger to bottom out keeping the contacts engaged until battery cable is removed

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A weak or broken plunger spring or a sticking plunger may also contribute to this problem. This problem is not too unusual on Delco starters. When the solenoid is energized the plunger is drawn into the solenoid and causes the switch under the cap to close. When power is no longer applied to the S terminal the spring moves the lever and in turn withdraws the starter drive from the ring gear. It also allows the switch to open and the starter motor stops turning. The load on the drive gear as it meshes with the ring gear keeps the drive from sliding back on the armature shaft. If there is a problem with the stop collar on the armature the drive may engage too far and there is not enough movement to allow the switch to open.

If the starter is removed from the tractor the load is no longer there and the starter will work like it should. Likewise it would most likely not show any problems if the engine were started. In that case as the engine started the load on the drive would be released and the solenoid plunger spring would be able to retract the drive.

I want to say thanks to all of you for helping. You have injected some ideas for me to check out. At least now I have a place to start from again. Maybe I will only have to pull it one more time. Again thanks to all of you for your help.
Thanks a MILLION,
Don (Sarah, my better half)

I checked the voltage on the S terminal. With the power disconnected after the starter started spinning there was 6.5 volts still on the S terminal. Here is what I have deducted:
The fly wheel is locking on to the starter gear and holding the solenoid in, keeping the switch in the back of the solenoid pushed in keeping power going to the starter. I have to get the flywheel to turn loose of the starter gear. I will try some grease of some kind on it. If that doesn't work I may shim the starter on the bottom to get a little more space between gears.
I did find out that if you keep bumping the ignition switch to start it will turn loose after a few bumps. Hope this makes sense.
Again thanks a bunch for your input.

I wouldn't think there would be any voltage on the S terminal when you let off the starter button or quit twisting the key. Hal

(quoted from post at 17:23:18 12/24/10) I wouldn't think there would be any voltage on the S terminal when you let off the starter button or quit twisting the key. Hal

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I would agree, she needs to pull the wire from that terminal and retest.

(quoted from post at 17:23:18 12/24/10) I wouldn't think there would be any voltage on the S terminal when you let off the starter button or quit twisting the key. Hal

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There are two coils in the solenoid, a pull in winding and a hold in winding. The pull in winding is connected between the S terminal and the solenoid output post which is connected to the starter motor. The hold in winding is connected between the S terminal and the solenoid case. Since the starter motor has very little resistance, when the S terminal is energized both coils become electromagnets and draw the plunger into the solenoid. When the plunger has moved in far enough to make the connection of the switch the pull in winding now has battery voltage on both ends and no longer serves as a magnet. The hold in winding continues to keep the plunger in the solenoid counteracting the spring pressure.

In the case of this starter the plunger is keeping the solenoid switch contacts closed after the power is cut off to the S terminal. Since the pull in winding is grounded through the starter motor, as long as the switch in the solenoid is closed the pull in winding will back feed to the S terminal and there will be voltage there. Since both windings share a common connection at the S terminal the voltage being back fed through the pull in winding now also goes though the hold in winding to ground. Total voltage drop across both windings will be equal to battery voltage. Since the S terminal is now close to the center of the complete circuit the voltage at that terminal will be somewhere around half of the battery voltage.