Replaced dead battery a few weeks ago. Upgraded to 750 cold cranking amps (old one was 650). Started great for two weeks. Now, sometimes it starts, sometimes doesn't. Cranks over but sometimes I can not hear the fuel pump kick in when I turn the key. I sit and rotate the key back and forth from auxilliary to start several times and then I eventually hear the fuel pump kick in and the truck will fire up. Runs great, no loss of power when accelerating, does hills and mountains fine, no engine missing or power loss. I checked fuse and replaced the fuel pump relay. This has happened about twenty times over the last two weeks. Truck hasn't left me sit, but it is a pain working the key and waiting for the fuel pump to eventually hum.