I have an '83 F-250 V8 diesel. A couple days ago I tried starting the truck and it was starting like normal but when I quit turning the key the starter kept going. Then it quit after a few seconds, so I turned the truck off to see if it did it again. This time the solenoid just clicked and the starter didn’t engage.
I’m probably an idiot for doing this, but I thought it was the solenoid because I replaced it recently since the plunger had been getting stuck and it kept trying to crank like that. Anyway, I put a screwdriver across the two main terminals and the starter started turning over, but it wouldn’t stop once I removed the screwdriver. I had to pull the battery terminals off(there are two batteries in the truck).
Anyway, since it was cheaper I just tried replacing the solenoid even though it seemed like it might be the starter or something else. Sure enough it’s still doing the same thing. Do I need to replace the starter?
I would guess that it is the switch assembly inside the starter, so yes a new starter is probably the solution. Just in case, you might try disconnecting the small control wire going to the starter relay (solenoid switch). Cross the load terminals and if the starter engages and then disengages when you remove the short, it might be something really odd with the ignition switch.
I wonder about my 03 blazer’ it seems a couple of years ago, or maybe only then I noticed that if I gave the shortest click to start it would automatically crank as long as needed until it starts. I need to ask when it kept cranking did the engine start? If the engine did not start maybe there is some brain that automatically controls the cutout of the starter motor. I actually like the feature but do not know if it is by design.
In conclusion your solenoid is probably toast, and if your engine does not start you need to fix it.