I have a 97 with the 5.7 vortec with 245 thousand miles. Recently I parked it for a day and came back and it wouldn't start. Cranks but no start. Changed the fuel filter, which the old one had sand in it. Still wouldn't start. Pulled off the connection on the ignition coil and put it back on. Then it fired up. Drove it for a day and parked it for about 18 hours. Went back and same thing, cranks but won't start. My battery is good, cranking amps are good, no codes, has spark and fuel. I have no idea what is wrong. Any ideas out there?