I have a 1990 Honda Accord LX, and the gas gauge always reads full, it doesn't move at all.


What could be the problem and how can I fix it without taking it in.

 

Whats the problem with having a full tank at all times? ROFL
All jokes aside; you need to open the round access panel behind the rear seat in the trunk and get to the connector for the fuel sending unit.
Unplug it, turn on the key and the fuel gauge should stay low [empty]. This would indicate a problem with the sending unit.
If you turn on the key and the gauge still reads full, the fault is more likely to be the gauge itself.
The only other thing COULD be the wire is shorting to ground "somewhere."
The gauge works by way of changing resistance of the sending unit, the lower the resistance the higher the gauge reads, and vice-versa.

 

So, by accessing the unit, and unplugging it, if it goes empty, I need to replace the unit, if it stays full, its shorting somewhere?

Supposedly, the guy I baught it from got a new cd deck installed, and he said the problem started after that.

 

If it stays full its either shorting somewhere or its the gas gauge itself.

You might want to inspect the wiring behind the new CD deck. There is a thread dealing with stereo installation and wiring in the DIY section.

 

That's a real good reason to suspect some wiring problem in the dashboard.

Still, do the check that hondadude said, becuase it's pretty easy to check.