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Jump starting

what may have my son fried by reversing the polarity while jumping the battery in his 95 GMC pickup? The smaller wire coming off the + terminal was burned through,so I spliced that. The engine cranks but there is no spark.

First three things tha come to mind are, anything powered off that small wire that burned through, internal components inside the distributor (do the “no-spark” test procedure from the manual) and the PCM. You do not mention if you have done a fuse check, people always say they did a fuse check.

Couldve fried ANYTHING electronic.

It’s at this point you hope that the protection mechanisms designed into the vehicle have saved your bacon. They’re not specifically designed to prevent damage in this situation but you can hope.

I would first check for bus voltage at the fuse box.
Bad- check the fusable links in the wiring harness.
OK- check all of the fuses.
Then check the ECM by at least seeing if it will respond to inquiry.

Hopefully, you will discover a fault by this point in the diagnosis…