89 Caravan LS 2.5 non-turbo weak spark

:x My van jumped timing on a cold start-up, the starter would'nt shut off so I replaced it. It started after I retimed it but the timing advance needed to be adjusted. It refuses to startnow. A spark intensity test shows a weak intermitent spark and sometimes no spark at all. I changed the coil, no change, I changed the cap and rotor, no change, I changed the ignition switch, no change still. All thats left is the wires and the sbec, so my question to you is, what is the problem? :X