I have a 1995 Ford f250 with a 5.8l engine. When you turn the ignition switch on, there is pressure at the fuel rail, as soon as you turn the ignition switch to start, the pressure goes to zero. You can turn the switch off and immediately turn to on and it will pressure up. It has two tanks and the result is the same with either tank. Have changed the coil and the fuel module. Any ideas?

. Check all under hood and under dash fuses with a test light or multimeter.

. Check for spark.

. Check/replace the ignition switch.

If the truck doesn't start, for even a moment, when the fuel rail is fully pressurized, the problem may be a bad Ignition Control Module (ICM). 90%+ of all crank but won't start situations are electrical related, not fuel. My bet, from afar, is that the ICM is bad. The spark is probably poor, non-existant, or not when the PCM needs it to fire.