Lull 944E-42, Service Manual

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9.243 Model 644E-42/944E-42 Rev. 6/04
Electrical System
4. Turn the ignition key switch to the OFF (8) position.
The fuel level gauge needle should return to the
EMPTY position.
b. Fuel Level Circuit Tests
For additional information refer to Section 9.10.11, “Fuel
Level Gauge Troubleshooting.”
If the fuel level gauge is suspected of giving a false
reading, perform the following checks:
1. Check for loose or defective wiring, faulty ground
connections, and corrosion on the fuel tank level
sender and wiring lead.
2. If the fuel level gauge needle does not move after
the ignition key switch (6) is turned to the RUN (7)
position, use a test lamp to determine whether
current is flowing from the ignition switch to the fuel
level gauge wiring connector behind the operator’s
dash panel.
If the fuel level gauge (1) needle does not move,
check the fuel tank for fuel.
If the fuel level gauge does not move and a faulty or
defective fuel level sender in the fuel tank has been
ruled out, and in addition, wiring and connectors have
been checked and ruled out, the front dash panel is
defective and must be replaced.
3. Check that the ignition terminal has current and that
the fuse in the fuse panel is not blown.
4. Check for broken, shorted, frayed, disconnected or
damaged wiring between the fuel level gauge wiring
at the operator’s dash panel, fuse and relay panel,
ignition key switch, and from the fuel level sender on
the fuel tank through the wiring in the cab.
5. Check the fuel level sender. The resistance of the
fuel sender is 31 ohms for a full tank of fuel, 101
ohms for 1/2 tank and 255 ohms for an empty tank.
A defective fuel level sender in the fuel tank may also
prevent the fuel level gauge from moving.
Excessive fuel level gauge “fluctuation” may be caused
by loose wire connections or a defective fuel level sender
in the fuel tank.
A full tank reading at all times may occur if the wiring to
the fuel level sender in the tank is broken, if the sender is
not properly grounded or if the sender is defective.
If the fuel level gauge appears to be inaccurate, the fuel
sender in the tank may be defective, or there may be low
voltage at the fuel level gauge connector to the operator’s
dash panel.
If the fuel level gauge fluctuates when other electrical
items are used, there may be a defective, corroded or
improper ground. Check the cab harness ground stud
under the dash, the engine to chassis ground, and the
negative (–) battery cable and ground stud cable.
Examine the fuel level sender circuit in Section 9.10.11,
“Fuel Level Gauge Troubleshooting.”
MU1250
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