hard starting turns not starting!
 

So we have this 02, cummins, replaced and bypassed factory fuel system with an air dog 150. Fixed p-rings at return line tee and banjo bolt washes. No fuel leaks. Batteries both charged and tested good. Started cranking slower and slower till no start. Never cranked more than 15 seconds at a time. All connections seem tight and are clean. Starter gave light puffs of smoke after 4 seconds of cranking. still cranks but no start? Any ideas as to if this is still a fuel issue or go straight to starter rebuild.......

if after 15 seconds starter slows down, and smoke came out of it, its likely failing, cranking speed is critical in a start.
i'd load test batterys and test starter

Replaced starter last night. It was bound to fail since a mounting ear was broken. Tried to start and the batteries didn't have enough juice. So replacing them today. Otherwise it started great when jumped. Had to be a failing starter issue. I'm guessing partly brought on by weak batteries and lots of cranking.