My 1999 Chevy Astro van won't run. Fuel gauge flipping out so I dropped the tank did the deal and it won't start. checked the voltage and with ground reads 5 volts body ground 12 volts. Why?

It sounds like you may have a problem with the fuel pump or the wiring related to it. The 5-volt reading suggests that there could be an issue with the fuel gauge sending unit or a short somewhere in the wiring harness. Additionally, check the fuel pump relay and any associated fuses, as they could affect the voltage being supplied. Ensure that all connections are secure and that there are no grounds or shorts in the system.