My Blazer cranks over and over...killed the battery : ...next morning the second time I tried cranking it over it made a poof sound and started but with a lot of chugging. Can anybody help please?

Lynda, If it is the 4.3 V6, they are prone to getting moisture in distributor which causes the symptoms you are talking about including the poof. You can have scanned to see if trouble codes are stored, you may get multiple misfire.
If continues doing this have cap and rotor replaced and if wires and plugs are old do them to. Check the attached links,instruction and guides, Good luck
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