Okay, I get in the car to run a couple of errands, start the car up, and the engine starts making a helluvalotta noise. I turn the engine off and I quickly figure out what’s causing the noise: the starter’s still trying to start the engine! I don’t mean, the bendix is acting wonky, I mean, with the ignition off, and the key out of the ignition, the engine’s still turning! It’s not getting any spark, but it’s quite clearly turning, and it didn’t stop until I yanked one of the battery cables loose from the battery. When I hooked the battery back up, the starter didn’t try to crank the engine, and when I started the engine up, it started normally. I’ve installed a cutoff switch on the battery, so that if this happens again, then I don’t have to spend time digging out my tools to kill the starter, but I’d like to know what caused this. The starter’s a rebuilt unit which was put on the car less than a year ago. Anyone have any ideas? (Car’s a 1990 Pontiac Grand Am with 170,000+ miles on the clock [the odometer and gas gauge take turns working].)
I’m guessing the starter solenoid got stuck.
That’s it. Make sure you don’t flip the battery disconnect while the engine is running, or your electrical system won’t like you.
Too late. All that happened was the car kept running. I really don’t think it’s a stuck bendix, though since the starter kept turning the engine with no key in the ignition, and it was most definately spinning. I could watch the belts turn.
Two possibilites
1.) Solonoid stuck
2.) The wire from the ignition key to the solonoid is shorting to 12V, and th esolonoid thinks you are keeping the key in crank.
Fix
1.) Replace solonoid
2.) find short and make it longer
Exact same thing happened in my car (92 accord) except the car just kept cranking after I replaced the battery terminal .
Pull the small signal wire which leads to the starter solenoid to confirm.
Some people said you can bang away at the solenoid to get it to stop, but thats obviously a short-term solution.
I just replaced my entire starter.
rick: if it was a short wouldn’t it start cranking up again after he put the battery cable back on?
Danceswithcats: I believe the car runs completely off the alternator once the engine is running. I’ve accidentally removed my battery terminal before and it kept running.
[preach]
It seems like you have alot of problems with your cars. When you get the cash, buy a honda! 
[/preach]
Many cars rely on the battery to do a lot of the filtering and voltage regulation. If you disconnect the battery you can get some pretty wild voltage fluctuations. Older, simpler cars are more likely to stay running. In newer cars, sensitive electronics (like the engine computer) can be damaged by the overvoltages.
ok, would my 92 accord be considered newer?
er, that might sound kind of snippy.
How about…
I stand corrected. Would my 92 accord be considered “newer” ?
Would my 92 accord be considered “newer” ?
Yes.
If it was a short wouldn’t it start cranking up again after he put the battery cable back on?
Whether it was a short in the named circuit or a something sticking in the starter, it would crank if the condition remained unchanged and not crank if the condition were intermittent. Either is possible.
99.9% probability it’s a faulty starter. The starter is likely under warranty, but regardless, I would replace it.
I seriously doubt that either the OP’s 1990 Pontiac or Harmonix’s 1992 Honda would be under warranty.
The warranty comment was directed to the OP. The OP said “The starter’s a rebuilt unit which was put on the car less than a year ago.”
Definatly a sticking solinoid. Beat on it with whatever falls to hand. First couple times this happened to me, I replaced the solinoid, now I don’t bother, as It seems to be a once in a blue-moon thing.
I had this exact same problem with a 2000 Range Rover not too long ago. I disconnected the battery, preventing it from starting, and when the battery was reconnected some hours later, everything was normal. We just wrote it off to typical British automotive electrical systems and forgot about it. Hasn’t happened since but then that truck has been under major (collision) repair for some time and is just now starting to be driven. If it happens again, we’ll take the time to troubleshoot it then (my guesses would start at the BECM).
I should clarify that my runaway starter problem began when the battery was reconnected after many months of not being connected. The key wasn’t even in the ignition when it began.