2002 Chevy Truck R&R starter, now no fire at plugs

My starter was bad. I replaced the starter which now turns over good however truck will not start and I have no fire at the plugs. There are wires in the starter wire loom that branched off to a sender in the pan and a set that went to what looked like the bellhousing. These wires look ok but may have been damaged inside. What are these wires for and can they keep the truck from starting? Thanks in advance. Larry