Fuel economy is not calculated based on the sender readings. It probably is a worn sender.
Gauge failures are often caused by defective wiring or grounds. The first step in locating trouble should be a thorough inspection of all wiring, terminals and printed circuits. If wiring is secured by clamps, check to see whether the insulation has been severed thereby grounding the wire. In the case of a fuel gauge installation, rust may cause failure by corrosion at the ground connection of the tank unit.
Disconnect wiring from fuel tank sending unit.
Connect wiring to a known good sending unit.
Connect a jumper wire between sending unit pick up tube and ground.
Check fuel gauge as follows: Allow at least two minutes for gauge to settle at each test point.
Move and clip float arm to its empty stop and turn ignition to the On position, gauge should read Empty or below.
Move and clip float arm to the Full position, gauge should read Full or above.
If gauge does not meet specifications, check the following items for possible malfunction:
Wiring and connections between gauge sending unit and multiple connector behind left kick panel.
Wiring and connections between multiple connector and printed circuit board terminals.
Circuit continuity between printed circuit board terminals and gauge terminals. If the above items are satisfactory, the gauge is defective and must be replaced.
If fuel gauge meets specifications check original fuel tank sending unit as follows:
Remove fuel tank sending unit from fuel tank and connect a jumper wire between sending unit pick up tube and ground.
Repeat step 4.
If fuel gauge is now within specifications, check the following as possible cause:
Ground wire from sending unit to left side cowl for continuity.
Sending unit deformed. Ensure float arm moves freely and pick up tube is not bent.
Sending unit improperly installed. Install correctly.
Mounting flange on fuel tank for sending unit deformed.
Fuel tank bottom deformed causing improper positioning of pick-up tube.
Wednesday, February 10th, 2010 AT 7:07 AM