Need help with a 85 4.3l

[mtnsackett]

I am having a problem with my 85 GMC 4.5 1500.

here is the issue, the truck has sat for at least 7 years and the engine turns over slowly, even with a new battery and a 50 amp charger on it. it seams to have weak spark. I have replaced the plugs, wires, distributer cap, rotor all the electrical components for the distributor. including the pickup coil and its still weak. I have checked to see if I have the proper voltage at the distributer and it checks out at 12.5 volts


if anyone has any ideas to help I would appreciate it, if I can't figure it out soon I think I will just replace the whole engine and wiring harness under the hood. but the dealership said this was kind of a rare truck and it would be a shame to chop it up.