1996 K2500 7.4 ltr. Left it sitting for about a week and battery was dead. It wouldnt even start with jumper. Took batery out (Red top Optima 2yrs old) and it took charge. Put it in and when I started truck, my girlfriend saw sparks emit from bottom of truck. I left it overnight and in the morning dead again. Put in new battery (Optima) and now truck just clicks when I try and start it. Cleaned both pos. cables and they look fine. Couldnt see the motor end of neg cable but its on tight. Alternator passed charge test at autozone. Dont know what else to do. With new battery starter clicks but only starts when I quickly turn key multple times. Please help.
