1989 Chevy Silverado after setting timing

Thanks Joe, The truck blew the gasket and the died. My friend fixed that problem, and when he drove it back in town it worked fine, when I got to drive it it started to act up, not firing right I drove it home and it quit running. I found the dis module was bad and replace it, then I set the timing with the dis bypass unhooked, when I connect the bypssa back up it runs but with no advance timming, and spudders and backfires. Looking at nthe wiring dia a signal wire is comming off the dis module back to the pcm, when I think it reads this signal and takes over the timing, but it is not doing it. The timing belt was never never took off, as far as I know. Thanks again Joe.