1991 Ford F-250 5.0L : The starter was just replaced with new one (about one month ago), than the relay went out today - I replaced it with a new one. With the new relay installed, I have started the truck up at least six times, but twice the starter stayed engaged while the engine was running. when I turned off the key, it stayed running. I had to disconnect the battery to stop the engine. The second time it stopped after a few minutes. Does anyone know what is causing this ? Is it the new relay ? Could it be the ignition switch ?

Hmmm? Starter solenoid is somehow staying empowered by a wiring problem at ign or along the way somehow. (is that what you meant by "relay?")

A solenoid can fail and stay stuck ON! If not new I'd toss it with an intermittent issue like this that can be VERY destructive!


T
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Tom Greenleaf - MetroWest, Boston












(This post was edited by Tom Greenleaf on Sep 4, 2009, 3:35 AM)

To add to Tom's suggestions;
If the flywheel/flexplate teeth have been damaged, the starter drive can 'hang up', causing it to stay engaged. Very rare, but I've run into a few where the battery voltage was too low to pull the starter drive back. I know. Sounds impossible. But, I've run into it.
Loren
SW WA