Had this same problem in January, changed FICM, IPR , Both Batteries and alternator then still no start changed the Starter and boom ran fine till last week.
Only mods SCT with Old Spartan Tunes. Ran thru No Start check list everything except air test, No air on side of the road.
FICM 47-48 Immediately
ICP Reads .70-.89 V at jumper on harness
No Codes LPO rises after 15 secs of cranking when ICP shows .7 it acts like it wants to start but wont fire. No smoke from exhaust. Pulled FICM OHMS checked all injectors both coils from FICM connector highest was #2 it was 1.8 Ohms all the rest were .7 to .8 ohms. Buzz test sounds ok.
Changed oil and filter T6 5-40W always
Both Fuel Filters, Primary little dirty secondary slightly brown.
Secondary fuel bowl fills in 4 secs no bubbles
Did the injector mechanical test with fuel bowl open no bubbles while cranking
Changed the starter again turns 340-360 rpm while cranking, Actron code scan plus no codes at all.
What am I missing????????