I have a 1977 F150 4WD, automatic. The starter fires up the engine, but then tries to run with it. It all began when the truck wouldn't start. I replaced the positive battery cable, then the negative cable end, next the solenoid, finally the starter itself. All were new parts. Now the truck starts and runs beautifully, except the starter won't cut out once it's going. Any suggestions or ideas?

 

IowaSky,

Every starter has what is commonly referred to as a "bendix drive". This is the mechanism that slides the starter gear back and forth. Before replacing the starter, you may want to put some hi-temp grease on the linkages that move the gear back and forth, It could be that yours is just too dry and not allowing the gear to move as it should. You can test this before you put the starter back on. Take a set of jumper cables. Ground the negative cable to the starter housing. Touch the positive cable to the starter lead. You should then be able to see the gear sliding back and fourth and spinning!. (You are actually simulating the starter gear engaging your flywheel or flexplate.)

 

also make sure you didn't cross the S and I terminals on the new solenoid...

 

Does it every time, like once it starts and you release the key out of the spring loaded "start position" and back to run? And you have to shut the key off to kill it/stop the starter? I would suspect a welded contact in the inside of the fenderwell mounted starter solenoid.

Better get it figure out ASAP, so you do not damage the fly wheel. X2 on take the starter off and do the jumper cable test as recommended above. Then I would replace the starter solenoid, new or not they get stuck "on".

Is all the wiring going to the ignition switch ok and not hacked up or cut up? I would suspect the starter solenoid, then the starter, then the ing switch. Has it been fine and then just started this issue?

(1ton basecamp) Also, one way to test the theory of it being a bad relay/solenoid/or the ignition switch wiring, is to pull the Red w/blue wire (the "S" wire) off of the relay while it's cranking uncontrolled. So the next time it sticks and keeps the starter spinning, pull the small "S" wire. If it stops the starter from spinning, then the problem is before the relay. If the starter continues to crank/spin, then the starter relay is faulty.

 

Actually, the key being return to run position does not stop the starter from spinning. I have to run around to the engine compartment and pull the wire off the S terminal. When I do, the starter disengages and the engine continues to run normally. So would this mean it is in the ignition switch? It appears to work like it always has. How would I test it?

 

That was a question I had.
So to my mind, that proves that the starter relay and the starter are not the issue.
If pulling the S wire stops the starter, that means there’s stray voltage on the S wire that shouldn’t be there when you release the key to the ON position.
The most obvious culprit then, would be the ignition switch itself.
However, that voltage could be coming from other places along the wire. Perhaps even the neutral safety switch where the back up lamps have power in the ON position and maybe something is crossing over to the red with blue stripe wire.
You’re going to have to trace the Red w/blue wire back and find out where the power is coming from.
It sounds like it goes away after all is said and done, or as soon as you reconnect it, the starter would crank again.
So this only happens after you turn the key to start and then release it. Something along the line is causing voltage to stay on the wire.

I guess the next test for me then, would be too leave that wire disconnected, and use your voltmeter or test lamp to simply test it with the key again. But not when connected to the starter relay.
Have a helper turn the key to start, then release it to on. See if the voltage stays at the wire.
A voltmeter would be better than a lamp I believe, so you could see if it even changes.
For example, goes from 12.2 V in start, to 8 V when you release the key.

 

New starter solenoids are junk out of the box.
I bet the contacts welded themselves closed.
Take something and hit the solenoid and see if that stops it.
If so go out and pick up a top of the line solenoid, you have to ask for it otherwise you get the cheap one. I run a NAPA top of the line about $50 and no issues in 4 years.
Welded contacts is common now days.
Dave ----

 

Pull both wires off the solenoid,turn the switch to on. One wire should have no voltage,the other should have around 6v. Turn and hold switch to start. The wire that previously had no voltage should now have 12v, goes on the S terminal on the solenoid. Like previously mentioned,this is if the wiring is original and not modified.

 

Another quick test:

1. Start engine
2. release the key so it returns to the [Run] position
3. I assume at this point the starter is still running
4. Slowly turn the key towards [Off]
5. Is there a point in this rotation where the starter stops and the engine keeps running?

If so, definitely the ignition switch.