I would try something simple 1st. It sounds to me like the fuel pump relay. Basicly there are 2 circuts from the pump to the TB. Ine goes through the oil pressure circuit. GM designed it so that if the system sensed no oil pressure then it would shut off the fuel. When you crank and crank the motor, you build enough oil pressure for the fuel pump to kick in, so the motor starts.
I had the same issue on my 88 350. After a lot of messing around that simple switch fixed it.
Not exactly correct. The oil pressure switch cannot turn the pump OFF. It can turn the pump ON even if the fuel pump relay or harness or the ECM fuel pump relay driver circuitry is defective.
The symptom of failure in the fuel pump relay system is a long "crank" time, generally in conjunction with no 2-second fuel pump prime when the key is first turned to "ON" or "Crank".
The FIRST thing would be to test fuel pressure--
assure there's a 2-second prime, and then that the fuel pump achieves proper pressure and volume while cranking and running. You'd want to verify that the pressure is within spec even under heavy load and high RPM.
If you have fuel pressure during prime and during cranking, I'd be looking at "tune-up" issues--failed cap 'n' rotor, weak coil, defective plug wires, fouled or worn plugs, etc.
NO fuel pressure until oil pressure builds, and no spark during cranking is likely the pickup coil in the distributor--although it's possible (not likely) to be an ignition module problem or ECM/wiring harness problem.
A scan tool to peek at the data stream could be very useful. I'd pay particular attention to cranking rpm, engine coolant temperature, and short- and long-term fuel trims.
