BMW Repair: 1991 525i, fortay, fuel pumps

Question
Hello, I stopped at the store and the car would not restart.  I knew I was not out of gas, but everyone else seeemed to think I was.  I put gas in it and it still did not start.  The car turns over and even caught once or twice, but it sounded more like "if I could just get a little gas, I can get going."  I have not had the car long and I did put a treatment in it when I got it.  Do you think it is a fuel filter, fuel pump or what?  If this car is not in your area of knowledge can you please tell me where to go.  Oh, yea, I had just driven home at about 80mph for 49 miles, stopped at the store, got back in and not start.  The gas was a little lower than I normally let it get.  When I first got the car it would start and I would press on the excelarator and there was no racing, just put-put, but it had not done it in a while.  I left the car and went back after two hours, still no start.  Please help me.

Answer
Phil- You need to figure out If you are missing fuel, spark, air, or compression. Compression is doubtful since the car can run. Pull an intake hose a squirt a little starting fluid in it and crank it. Does it sputter or start for a second? If that doesn't work pull a spark plug and reconnect to it's boot and hold it by the boot. Put the plug end on an good solid metal grounded object. Have someone crank the motor while you check for spark at the plug. Do you have a good health spark? Fuel pumps are common on these cars it has two. Bang on the bottom side of the passenger side fuel tank. Does the car start now? Check the fuel pressure. E30 is not my fortay so you might ask one of the other older experts. Fill out a follow up survey if any of this helps you. Good luck.
-Evan