Without knowing any details about what its doing.....this is what it should be doing.
When turning the key to the ON position, the fuel pump should prime cycle for 2 seconds.
When turning the key to the ON position and only "bumping" the starter with the key over in the START position, the fuel pump will cycle for 25 seconds.
Cranking the engine to start, the voltage from the ECM to the fuel pump will alternate on/off in order to reduce fuel pressure by approximately half.
As soon as the engine starts and runs, the voltage to the fuel pump will be constant 12 volts as the pump runs continuously.
If its not doing anything just said then there may be an ECM issue or the connector from the ECM to the fuel pump is no longer getting voltage signals. Not terribly uncommon as people have found that they have to wire the fuel pump to another hot source with a ignition triggered relay. No ones really sure why the ECM can do that either but its either corrosion, loose connection, or voltage load too high and destroying that particular circuit.
But if all above is working and:
If the engine experiences a hard start when the engine is cold and has been sitting (like overnight) then its most likely a fuel leak causing the prime to be lost. The extra cranking is merely re-priming the fuel system.
If it hard starts when the engine is at operating temp and temporarily shut off but doesnt want to re-start easily, then there's possibly two reasons.....
1) The PSG solder is crystallized from excessive heat cycles and fuel pressure too low.
2) If there is an aftermarket fuel pump on the truck then the fuel pump is too aggressive and is placing too much fuel pressure on the VP during engine cranking, even with the alternating voltage.
There are a couple other reasons based on the trucks condition and current setup, and having a fuel pressure gauge in cab or test gauge will help too. So maybe you can make something of that info but let me know what you find out. :Cheer: