I just bought a 2004 hyundai elantra. Apparently the dealer had just changed the oil and overfilled it by half a quart before I bought it. But I didn't discover this until driving 150 miles at which point the oil light started flickering and then went solid. (coincidentally the check engine light came on with two minutes of the oil light and gave the p0010 for camshaft actuator circuitry). The car also emitted blue smoke on startups.
I removed the excess oil, but now the oil light will still come on after about 10 minutes of driving. Is my oil pump destroyed?

 

An overfill of half a quart will not cause the problems you are experiencing. The oil light is for low oil pressure. Sounds like your pump is going bad or the filter is too restrictive. If you are getting blue smoke on startup then the car is burning oil. That doesn't come from a half quart overfill. That comes from a worn engine.

Bottom line, I think you bought a car with a bad engine.

 

Dang it.After removing the excess oil it seems the blue smoke on startup is gone. My question is why it took almost 200 miles for the oil light to come on after they overfilled it, where now it always comes on after 10 min of warming up...?

Additional question:
The battery only reads 10v when the car is off, and 14v+ when running. That's a bad battery right? Would that explain a mid-driving stall?

 

You don't state how many miles your engine has on it currently. If a high mileage car I would do a compression check to eliminate the worn engine possibility. Pretty rare that an oil pump dies unless you have a ton of miles on that engine.

Your alternator puts out around 14 V when the engine is running. To determine if the battery is headed for the dump you need to load test it with the proper equipment.

Battery life is around 5+ years, less if the car sits a lot. Sometimes a modern float charger can bring a battery back to life if left on the car for enough time to recondition the battery. But if its an old battery change it out before you get stranded.

Let us know the solution when you determine the problem, its an interesting issue.