I am a little unware here still of what exactly is going on. If I am right you are saying the motor is turning real slow and then not turning at all, its not a fuel issue but more a power or starter problem. If you tested the battery again, even though its new it can be bad if you originally had a alt. problem or if the battery was bad or if it is just drained low. Otherwise its a bad starter or lack of power to the starter. Right now you have to look at why the starter is lacking power is it bad or the is it not getting enough power. This means that at the present time the issue is not the alt, it may have caused it, but it isn't the reason why its not turning over. Most likely the issue is with the starter whern the battery is new but you alwasys want to check before purchasing the parts. Thanks again fot the question and if you have no further question please remeber the experts do not get paid unless you select accept.
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If this was helpful to you please select accept, and if you have any other questions please do reply. Thank you Eric