gas gauge help

[69swbman]

ok, i just replaced my fuel tank in my truck and now the gas gauge dosent work i hook it up and drops to empty, un hook it jumps well over full, also when the truck is off its registering little over empty when i go to start drops back to empty so any body know what the deal is? i was happy when it worked now im what the fu** also still used the fuel sending unit that was in it

[HoupPhotography]

Make sure the fuel gauge and the sending unit in the new tank have the same ohms, make sure you have a good ground.