I have a 2000friend chevy 2500 classic with a 5.7 engine. When it runs its perfect. Sometimes I start it and it dies and may not start again for a day. It will crank and crank but won't start. Something is killing the fuel pump and ignition. Not the background lights but all the other dash lights won't even light up and the battery gauge reads dead. Any ideas? So frustrated!

. Remove and fully charge the battery. Most auto parts stores will do this for free.

. Clean battery terminals and cable connections.

. Check for codes.

. Test all under hood and under dash fuses with a test light or multimeter.

. Check the ignition switch for wear, pitting, or melting--it may be bad.

. Focus on the Ignition Control Module (ICM), if the problem persists. I recommend replacing these problematic components every 120,000 miles or 10 years, whichever comes first.

Are you certain it's losing both fuel pump and ignition?
How are you testing for fuel pump or ignition?
Is the Check Engine Light (CEL) showing on the cluster when you cycle the ignition key to ON? Does it stay on when the engine does start?

I would start by looking very closely at the battery and battery cables. If that is equipped with a side post style battery, you may have a battery that is going to fail right at the terminal where the cable bolts on.
Try removing each cable at the battery and insuring they are sound, clean and tighten properly. Both ends of both battery cables needs to be free of corrosion, clean and tight.

Sorry it took so long to get back on here. I replaced the ignition switch and fixed all my problems. Thanks for the help

Good job.