Chevrolet Repair: My Blazer wont start..., vacum leaks, chevy blazer

Question
I have 98 Chevy Blazer 4x4 with a 4.3L. I recently had a coolant leak in the intake manifold, so my boyfriend fixed the leak. Problem is after he put everything back together it wouldn't start. He replaced the distributor cap, made sure the plug wires were in the right order, but it still won't turn over and it sometimes backfires when he tries to start it.
He also found a wire from the harness that wasn't connected and can't figure out where it goes. It has a light blue end. We are hoping if he can find out where the wire goes it will fix the starting problem.
Any help would be greatly appreciated and thanks in advance.

Answer
Hi Krissie... that wire may not have been plugged into anything... look at it and see if it's clean like it had been plugged in... if end is all dirty then it probably wasn't... there are wires under the hood for options that your truck may not have....did you remove the distributor or just change the cap....a backfire would tell me something is not right. check firing order again...if your still not sure about plug in i would suggest finding another truck the same and look and see where plug may go...local wrecking yard would be a good place to go and look....also make sure you don't have any vacum leaks...hope this helps