Check Engine Light-Diagnose for FREE!

Are you running it on the old fuel that was in the tank? Old fuel can go 'Off' leaving a varnish like layer on the injectors and valve seats. Drain all the old fuel out and run only fresh fuel.
Try cleaning or replacing the spark plugs. Change the Fuel, Fuel filter, Air filter, Oil and Oil filter. Basically, give it a major service. This helps make sure your getting good fuel, clean air and strong spark.
When it does start you could run some injector cleaner through the system.
*Note*, Run the vehicle at idle with the cleaner. Don't "rev it up", as revving thins out the mix of fuel and cleaner.

It could be a bad mass air flow sensor , try tapping on the on it .

There is basicaally only three things that can cause this:

>FUEL
>IGNITION
>COMPRESSION

he fuel system consists of two major systems: The fuel DELIVERY system and the fuel INJECTION system..Unless we are talking about an old vehicle that is equipped with a carburetor. (You did not mention what type of vehicle - which would be nice if you actually expect somebody to help you).

The ignition system is the spark plugs or glow plugs and all the other related components like the coils, wires distributor cap, rotor, distributor etc. Again, what components your vehicle is equipped with depends on the vehicle.

Compression is pretty much a mechanical issue - bent, burnt, broken valve train components, worn out piston rings, blown head gasket, broken timing chain or belt, etc.

The first thing you must do is determine which of the three basics is missing. Most modern automobiles have computers that control the fuel and ignition. To properly diagnose those systems on most vehicles, it is necessary to scan the onboard engine control computer.

You could try diagnosing and repairing whatever problem you are having by using methods prescribed by automobile repair industry standards. (Which, incidently, do not include "banging on motor")

1. Define the nature of the problem: What is the vehicle doing or not doing that indicates that the vehicle is malfunctioning?

2. Isolate the system: Which major system is malfunctioning? Is the problem being caused by the ignition system, The fuel delivery system, The fuel charging system, the brake system, Suspension system, etc.

3. Pinpiont the cause: What is wrong with the system that is causing it to malfunction?

4. Repair the malfunctioning system: Perform repairs to correct the cause of the system malfunction.

5. Verify the repair: Retest system to verify that the repairs performed were effective in correcting the malfunction that the vehicle was experiencing.

Step #1 in any automobile diagnosis is "Isolate the system"
Switching fuel tanks may have seemed like a good idea, but it did not definitively determine whether the the fuel is getting to the fuel rails, so you are no closer to eliminating the fuel devery system than you were when the engine died.
If it does it again, you should do the easiest things first.
Pull a spark plug wire and check to see that you have good spark reaching the spark plugs. Good spark will eliminate the entire spark control system.
Only if you have good spark should you suspect a "part-time " fuel system problem. The Fuel delivery system can be eliminated if actual fuel pressure is checked at the fuel rail. (although you could still have injectors not firing for one reason or another)
You are losing one of these systems. (spark or fuel) only once you have determined which one, can you continue diagnosis to pinpiont the failure.