Check valve in the pump, regulator, or injector(s) will all bleed fuel pressure.
This may help. http://performancefuelsystems.com/tech-leakdowntest.html
Basically if you hook a gauge up, start it then shut it down, watch to see how quickly if at all the pressure drops off, if it's quick it will most likely be the regulator or check valve in the pump, if it's slowly then it's an injector.
Need to check the fuel delivery problem also, see if the injectors are firing normally at start up, to check them you can rent noid lights from most auto parts stores. Simply unplug the electrical portion of the injector and plug the lights in, watch to see if they flash or not.
A quick way to check and see if it's a fuel system problem or a fuel delivery problem is do this.
Let it sit for awhile, turn the key to the ON position, but not start, listen for the fuel pump if you can hear it, if not give it 5 seconds in the ON position, then turn it back to off, then just for good measure do that cycle one more time, after that try and start it normally, see if it starts any better. If it does then is a fuel pressure/system problem.
Another thing to check is for external fuel leaks, it may be leaking someplace that isn't noticeable, also when was the last time you changed the fuel filter?
Like the other said the electrical system for the most part is on or off, it works or it doesn't and the fuel pump is the same, very rarely does a fuel pump start to go out or work intermittently.
Another thing to check for good measure is the condition of your battery, it may not be in good enough health to run everything properly, a weak battery causes all kinds of weird issues in some vehicles. Most auto parts stores will load test them, on or off the vehicle for free.