[LayneP]

When you turn the key to the ignition position, the fuel pump runs for a few seconds to pressurize the fuel system. Your ignition switch might be cutting power off to your ignition system or fuel pump when it is returned to the run position after starting. Try starting it and softly returning the key to the run position or wiggling it slightly back and forth mostly toward the crank position. If this doesn't give you the answer, another thing to try is once you get it running, have someone hit it with starting fluid near the end of your "3 second" run and see if it will keep running. If so, it is a quick confirmation of good ignition and no fuel supply, or if it dies, it is confirmation of no spark. This will point you the direction you need to go. Good luck!