I have a mind bogling problem with a 92 5.0 mustang. when you turn the key on the fuel pump is suppost to turn on, run for a few seconds than shut off. the one ive been working on will not shut off. i have installed a brand new gas tank, fuel pump, fuel filter, injectors, fuel regulator, and relays. occassionally after sitting the car will run. when you turn the key and the pump shuts off the car runs awesome and has no problems. no body can figure out what the problem is with this car i need some help any ideas?