Mine did the same after setting all winter. Change the fuel filter, cant leave it out otherwise it "senses" there is nothing there and wont let fuel in the motor.
Next charge the batteries and leave the charger on boost and crank her over . It will start up. One battery is probably weak. This is a school bus motor and has to turn over 5-6 times strong to get it started.
Plus make sure fuel level is over a 1/4 full.
- F250 SRW 7.3 crew PSD, 6" lift 38" toyo's. BTM, balwin filter. tru-cool. Gauges.
-F450 ZF6 flatbed, reg cab 4:88