Van made a loud pop like a backfire and the engine died on 1990 Chevrolet Astro

We have replaced the Pick up coil in the distributor, the coil, the cap and roter and the ICM module. The van won't produce more then a yellow spark at the distributer wire 1 x per new try. Almost every thing has been replaced and we are still scratching our heads. We don't have any other Ideas can you help?

Asked by for the 1990 Chevrolet Astro
Check crank sensor and PCM next. What are OBD codes?