2007 S60 owner here. My car has had a problem for the past 4 days where the engine will turn over, and sometimes almost catch, but I can't get ignition. The battery is completely fine and giving me full power, the fuel pressure is fine.

My father in law did have the idea to spray some starter fluid into the air filter as I turned the key, and that got it to start. It continued to start for the next 30 hours or so, but now refuses to work again, even with the starter fluid trick. I'm not sure if that was a fluke.

Any ideas at all? I'd like to try to get this fixed myself if possible, because taking it to a dealer means paying a tow fee and not eating for a couple of weeks (depending on how much they feel like overcharging).

edit: One thing I left out that I didn't think was relevant, but I guess may be. Last time I got my car inspected (2 months ago) they changed one of my headlight bulbs. I've had no reason to open up the hood since besides checking fluids, so I didn't notice it before, but when I was poking around in there due to the starting problem I noticed that they had left a bundle of wires loose. It's the bundle that feeds the passenger side headlight, and they had simply unclipped it and left it hanging, so it was rubbing against whatever it was near and some of the wires were worn clean through. After shifting it, the passenger side headlight no longer works. It's clipped back into place now, and I plan to fix it once I can get the more serious problem out of the way. I figured I should mention it just in case it could possibly have anything to do with my problem.