Still sounds familar
This thread is sounding mighty familar each day. As was mentioned in an earlier post, was the engine cranking strongly using two batteries or just a normal crank? The question I have is whether you took the battery out and to anywhere to check for a bad cell? I've seen them come right off the rack new with a bad cell, hence no cranking amperage, only voltage. The other end of the deal is the starter where I was stumped on mine. It cranked slowly over regardless of new battery or freshly recharged old one. End bearings start going out in those starter causing it to draw even more amperage while trying to overcome friction and basically you lose cranking power real quick, and never achieve enough rotation to get compression where it needs to be for combustion. Changed out the starter and lubed the upper cylinder with oil, and a way we went and started right up. Haven't had a problem since the starter change.