The fuel cut off switch is designed to shut off the fuel system in a collision it is a safety feature. The push button switch does fail from time to time and it can cause the problem you are describing. There is a simple method to test it's sensitivity, all you do is whack the body of the switch with a screwdriver handle and the switch should pop up. When you reset the switch you should feel some resistance when you press the push button, if there is no resistance the switch needs to be replaced.
post back your findings.
" What were dealing with is the battle between the future and the past, between the powers that were and the powers that have yet to be. " --- John Perry Barlow