If you need to replace the fuel sending unit you are in luck! This is a very expensive operation at an auto shop but it's really simple. You don't even need to take the tank out from under the truck. First you might want to make sure that this is really your problem. You want to get a good close look at your sending unit to see if there are any signs of deterioration. Read on, I'll show you what to look for. But before you get started taking things apart:
**LET FUEL PRESSURE MINIMIZE BEFORE REMOVING FUEL COMPONENTS AND FUEL LINES: WAIT A COUPLE OF HOURS FOR THE EXHAUST TO COOL DOWN WITH THE FUEL CAP OFF** Working on your vehicle is not fun with a hot engine and exhaust system!
The top of the fuel tank can be accessed from under the rear seat on the passenger side of the Xterra. To get to the sending unit you simply remove the rear seat and pull up the carpet access pad to expose the cover plate. Up until this point all you need is a 10mm socket or wrench.
Here is the cover removed and you can see the fuel connections and the electrical wires. One plug is for the fuel pump itself and the other plug is the for fuel level sensor. The fuel lines are simply fuel in and fuel out. I highly recommend you clean things up to make the connectors easier to see and remove.
Believe it or not, the fuel lines are easy to remove. You squeeze the sides of the lime green plastic retaining clips and pull at the black fuel line connectors to remove them. The electrical connectors are normal connectors that can be removed easier if you have a very small screwdriver to bend the tabs up while you wiggle them free.
Since it's the first year model Xterra its a little dirty at this point.
Do yourself a favor and clean things up a little and MAKE SURE you remove and wipe away any dirt or rocks that can fall into the tank once the unit is lifted upwards.