Fuel Gauge Problem

[Pratt]

My fuel gauge always reads full on my 2001 Super Air. I have changed the sending unit but it did not resolve the issue. I have checked all the wiring to the gauge and everything seems to be in working order.

To clarify things the gauge does move slightly, but it is only about 1/8" from slap full to totally empty.

Any ideas on how to remedy? Is it a bag gauge?

[jbach]

you should be able to pull the sending unit/float out. i'd start with verifying that it is working out of the tank. if it works out of the tank, it's either oriented the wrong direction in the tank or has some type of obstruction. if that doesn't worrk, see below, i copied and pasted from a previous thread.

MARINE FUEL SYSTEMS
COPYRIGHT 1998 TELEFLEX, INC. (USA)

1. Voltage - “I” to “G” terminal - 10 to 16 volts.
2. Test the gauge’s operation by doing the following: Connect a “hot” wire to the “I” terminal and ground wire to “G”
terminal. Take the sender (usually pink) wire off back of gauge . Gauge should read below Empty. Next, add a short
wire from the gauge’s “S” (sender) terminal to ground. Gauge should read above Full. If the pointer sweeps back
and forth, the gauge is OK.
3. The sender can be tested by checking its resistance with a volt/ohm test meter (use analog meter).
Remove sender (usually pink) wire from sender .
Connect two test meter wires to two sender terminals (or center terminal & flange if sender has only one terminal).
Move float arm by hand. Approximate values:
Empty = 240 ohms, 1/2 = 103 ohms, Full = 33 ohms.
(Not all Fuel Senders have the same resistance range. Marine units, either boat-builder installed or pur
chased at marine stores, are 240-33 ohms. Non-marine units may be 0-90 ohms, 73-10 ohms or some other
value.)
(Teleflex marine sender - rheostat housing installed upside down will cause gauge to read backwards. See
drawing on right above.)
4. Sender resistance tolerances at full may cause the gauge to read 2-3 pointer widths either side of the full mark.
5. The sender will accurately operate only one standard gauge at a time. It is not designed for dual station use with
standard gauges.
6. Fuel gauge will not operate accurately from more than one sender at a time. Some installations use a switch to
connect one gauge to various tanks, one at a time.
7. Sender will not operate in water tanks. Rheostat will become electrically “open”.
8. Be certain sender dimensions are adjusted per the instruction sheet.
9. If sender is “open” (infinite resistance), gauge will read below empty. If sender is shorted (0 resistance) gauge will
read above full.
10. Some “bowing” of the flange may occur when the 5 mounting screws are tightened. The gasket under the flange will
normally seal the flange properly, but do not over-tighten the mounting screws.
11. Sender must be grounded. No ground will cause the gauge to read empty.