It's not the fuel filter. The screen is on the end of the pickup tube inside the gas tank. It takes a while for it to collapse while driving so it typically won't cause a no-start condition. When mine created a problem, it was packed with rust-colored mud.
It IS possible for the pump to fail to start up when you try to start the engine, but you would find 0 psi at the test port. Banging on the tank while a helper cranks the engine will often get them started. You have a good clue that there is spark because it will run on starting fluid. Having spark rules out a problem with the sensors that must work for the fuel pump to turn on. Another potential clue is if you can't hear the hum of the pump for one second after turning on the ignition switch.
Based on your description of the problem, the best test is to monitor fuel pressure when driving or when trying to start the engine. That way you'll know for sure which system needs to be diagnosed. The pressure can check fine in the shop during a quick check, but what's important in this case is what happens when the problem acts up.
Saturday, March 5th, 2011 AT 8:30 PM