Why won't my Montana start?

I have a 2001 Pontiac Montana. Ive been having some trouble with it. When it starts I have to give gas right away to prevent it from dying. if it does die, it don't start back. It has done it 3 times now, but months aparts. what I have done after it not starting is: I checked the fuel rail. definitely getting gas up top. pulled the plugs and checked for spark. Getting spark at the plugs. (however not sure what the intensity of the spark should be, but I do see spark.) twice I pulled a plug, checked it for spark, put it back in and the van fired...luck maybe? This time I tried and it didn't work. The plugs seem dry for the constant turning over. Figured the plug would be wet. Could it be that the fuel is making it to the rail and the injectors are not firing? Is there anything I can do to check?