93 320i not turning on.

I've had my 320i for about 2 years, never had a problem with it running. My dad needed to borrow the car, so he dropped me off at work. On his way back from dropping me off, he stopped by the post office, and when he went to turn the vehicle back on, it wouldn't. It seemed like it would turn over, but not completely on. Since this is my first BMW, I'm not sure where to even begin. I ended up getting it towed back home, and looked at it this morning. If we spray starter fluid into it, it turns on briefly, so I'm not sure where to go from here. Could it be the fuel injectors, fuel pump, or fuel pump pressure regulator? I called for parts on it, and it has 2 fuel pumps (a left and a right) how would I know which one is faulty? Please help! This is the only means of transportation I have right now, and I dearly need to get it fixed before work tomorrow!