Could be the start stop or fuel solenoid located on rear of injection pump. Someone just had a similar problem, only one of the two wires hooked to it, came off.
Cummins manual states: Engine cranks but will not start- no smoke from exhaust:
no fuel in supply tank- check
electrical fuel shutdown not open- check for loose wires and verify that the valve is functioning, check to be sure that manual shut off lever is in the run position
air intake or exhaust plugged- check
fuel filter plugged w/water, other contamination/gasoline- drain fuel/water separator and replace fuel filter
injection pump not getting fuel or fuel is aerated - check fuel flow /bleed fuel system
worn or malfunctioning injection pump- visually check fuel delivery w/an externally connected injector to on of the pump outlets. replace pump if fuel is not being delivered
internal pump timing incorrect- verify/time the pump
camshaft out of time- check/correct gear train timing alignment
Anymore? I think we need more info to fix or diagnose this situation... Bill