my fuel gauge in my 95 ex sedan doesn't work at all... it stays at the full position all the time. Sometimes, very rarily, i'll hit a bump and it will work for a few minutes. what could be the problem?

 

under your back seat is the fuel pump cover. Its silver. Under it is the fuel pump and the fuel level sending unit, thats what tells you your fuel level. If you have a manual of any kind, helms or haynes, it will discuss what to do.
If not here is the basic idea.

If you take the sending unit out, its the one that has the brown non bent connector, connector has spots for 3 wires, but ony has 2. measure the resistance with an ohm meter across the gauge. When the tank is empty the resistance should be a 150-155 ohms. When its full it should be 2 to 5. If this isnt the case or the ohm reading doesnt change as gas is added to the tank, then replace the fuel level sending unit.
Good luck.