I had the same issue with the 98 S-10 Blazer I sold to Hal JR. After replacing the battery, and altenator. Both always tested good. Well I spoke with an older guy at Advance and he said his starter on his S-10 pick up caused him the same problem. Come to find out, I got under the Blazer and had my son try to start it, and thats where the spark show started. The cables were tight and no breakages. Took it to Advance they put it on the machine and it would throw sparks again. Replaced the starter and no more problems. Now how it draws on the system while not spinning or being engaged I don't know. The starter had a major draw on the electrical system just parked and the key in your hand. So you could be having the same starter symtoms. If you do have to replace the cables they are right use good quality cables, but I soldier all connections, and I don't crimp nothing. Good luck..
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When the people fear the government, there is tyranny. When the government fears the people, there is liberty.
Thomas Jefferson