My 85 C-4 with 38,000 miles starts on the third crank, runs a few seconds then quits.. No trouble codes.. If I pump the gas I can keep it running but it takes until the motor warms up to temp before it'll run on it's own.. (then rough).. The last time I drove it, it stumbled then smoothed out and ran fine.. The next day It started then died..Anyone have Any insight. I've drained the gas tank changed the filter checked the injectors for resistance..(All are 18)... Help!