Tonys 64 El Camino

This is in a '64 El Camino, '95 ECM, '95 4L60E trans, PCM setup for no EGR, NO MAF, NO CATs. fresh motor, new ICM, coil, wires, MSD Opti, This motor started and ran perfectly until 1 month ago, elect water pump failed and it got a bit warm(240), shut it down immediately, then the hard start began. Tried 2 ECM's same results. NO CODES. All elect. systems check out normal to Opti and to ICM and power to coil. I have SPARK at plugs. Fuel press 42 and holds solid, also tested during one of the engine runs. Noid light chkd all inj, good res on Inj coils. Did pulse test on inj. with press on fuel rail, all are opening and sealing. When motor does start it runs perfect, shut it down, it will not restart. Sometimes it will run a few seconds and die or just crank and pump fuel. I also replaced coolant sensor even though old one seemed to chk out fine. Baffled... Not sure if the MSD OPti is screwing me?