Start after storage

There's a bad connection somewhere. Check the connections on the starter as that's where GM ties in with the wires feeding the rest of the truck. Don't overlook the cable connections on your new battery. Also check the small black wire from the battery negative cable where it is bolted to the inner fender or body. If you don't find the problem, have a test light or digital voltmeter handy when you holler back.

Once you get the problem to appear, either by trying to start the engine or by turning on the head lights, leave whatever you turned on, on so the problem doesn't have a chance to correct itself. I like to leave the head lights turned on so I can watch for a change in brightness when I wiggle wires. Use a test light or voltmeter to measure the voltage at the bolts holding the battery cables to the battery. You must find at least 12.0 volts or the test light must be bright. If not, clean and tighten those connections.