My fuel data system has went out it comes on sometimes and goes back off

Hello, There are only two possibilities here. First, the fuel data center could have an internal issue and there are rebuild services available to restore it to functional condition. Next, you may have a poor connection, damaged, dried, cracked, or chewed (rodents) wires, or the connector has become fragile and cracked. I recommend removing the unit from the dash panel, inspecting the connection and wire harness, and seeing if manipulation of the wire harness causes the unit to gain/lose power.