I have a 96 F 250 diesel that cranks but will not start. It started off by dying when I would take my foot off the pedal. Would start right back up. Finnally after about 5 minutes of stopping and starting it quit starting. I've changed the fuel filter, changed oil, broke loose the banjo nut on the fuel pump while it was being cranked to check for fuel which it has at that point. Exhaust is clear when I crank the engine. There is air coming from the exhaust. I've checked for blown fuses, bad connections. It acted like it just ran out of fuel gradually and that was it. Any ideas? Thank You. Dan