I have read a lot of Forums and FSM. I have a 91 3.0 truck had blown head gasket. I replaced engine with a rebuilt long block. I have checked distributor (Good,) I have CEI with codes 12, 31, 14. I have !2v at Igniter and coil. I have replaced COIL with new. No change. I can remove distributor and spin the shaft with my hand I have good spark, once installed back in the engine I have no spark when spinning the engine over with starter. I have checked ignition.