An engine needs spark, fuel, and compression to run. If any of those are absent, it will not work. It is probably not a fuel problem, because the starting fluid didn't help. That leaves compression and spark as the remaining possibilities. I would check for lack of spark first, because that is more likely than a compression problem.
Get a clean spark plug (preferably not taking one out of the engine), take one of the plug wires off a spark plug that is in the engine, and connect the wire to the plug you just got. Place the plug so that the threaded part rests on the metal of the engine. You may need to clamp or tie it to the engine, so that it has a solid contact with the metal, and will not fall off. You can also press the plug against the engine with a block of wood; but do not touch it with your body or with a metal object. Have someone try to start the engine, while you watch the plug. While the starter runs, there should be a series of sparks which jump the gap between the plug electrodes. If you see sparks, then repeat this test on the plug wires from the two cylinders which are next to the one you first tested. If you get a spark from the wires on three adjacent cylinders, then you can assume the other three cylinders also are getting a spark. If you do not get any sparks, then you either have a computer or ignition problem; or the timing drive has broken. If you only get sparks from some of the wires, then you probably have a bad coil
If you do not get any sparks from the wires, then I would first check to see whether the timing drive has broken. One easy way to check for a broken timing drive is to remove all the spark plugs, and insert a compression gauge into the spark plug opening for each cylinder in turn. Have someone crank the starter and hold the accelerator pedal all the way down, while you are watching the gauge. The gauge should read at least 140psi. If it reads less than 100psi in several cylinders, then the timing drive has probably broken. You can confirm that the timing drive has broken by removing the valve cover, and then having someone run the starter while you watch the valve springs. If the valve springs do not move up and down when the starter is being run, then the timing drive is broken.
If you got sparks, and you have good compression, and the timing drive is not broken; then the spark plugs are either worn out or fouled, or there is a problem with the fuel injection system, a sensor, or the computer. Try replacing the spark plugs. If that does not help, then you'll need to get the computer, sensors, and fuel injection system tested.
If the fuel gauge reads empty while you know there is fuel in the tank, then the gauge wire at the tank has probably been disconnected; or the fuel has all run out of the tank while the pump was being replaced.
I hope this helps!