JLG sky trak mmv Service Manual page 649

3. From the operator's position, turn the ignition
switch (6) to the RUN (7) position. DO NOT start the
engine. Observe the fuel level indicator bars on the
operator's display panel. The reading must be at the
FULL mark, with all four bars illuminated after the
engine start-up bulb test is completed.
7
4. Turn the ignition switch to the OFF (8) position. The
bars should turn OFF.
Note: The cab must be partially removed to access the
fuel tank and fuel sender. Refer to Section 3.2.3, b. Cab
Removal in this manual for cab and fuel tank removal
instructions.
b. Fuel Level Circuit Tests
For additional information refer to Section 10.9.7, Fuel
Level Indicator Troubleshooting .
If the fuel level indicators are 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 sender
and wiring lead.
2. If the fuel level indicator bars do not illuminate after
the engine start-up bulb test is completed and when
the ignition switch 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
indicator wiring connector behind the operator's
display panel (the panel can be unfastened and
raised slightly to do this).
Model MMV Rev. 12/04
6
8
MM4760
3. If the fuel level indicator bars (1) do not illuminate,
check the fuel tank for fuel.
4. If the fuel level indicators do not illuminate, and a
faulty or defective fuel sender in the fuel tank has
been ruled out, and wiring and connectors have
been checked and ruled out, the operator's display
panel is defective and must be replaced in its
entirety.
5. Check that the ignition terminal has current, and that
the fuse in the fuse panel is not blown.
6. Check for broken, shorted, frayed, disconnected or
damaged wiring between the fuel level indicator
wiring at the operator's display panel, fuse and relay
panel, ignition switch, and from the fuel sender on
the fuel tank through the wiring in the cab.
7. Check the fuel level sender. The resistance of the
fuel sender is 33.5 ohms for a full tank of fuel and
240 ohms for an empty tank. A defective fuel level
sender in the fuel tank may also prevent the fuel
level indicator bars from illuminating.
Excessive fuel level indicator bar "fluctuation" may be
caused by loose wire connections or a defective fuel
sender in the fuel tank.
A full tank reading at all times may occur if the wiring to
the fuel sender in the tank is broken, if the sender is not
properly grounded, or if the sender is defective.
If the fuel level indicator bars indicate inaccurately, the
fuel sender in the tank may be defective or there may be
low voltage at the fuel level indicator connector to the op-
erator's display panel.
If the fuel level indicator bars fluctuate when other electri-
cal items are used, there may be a defective, corroded or
improper ground. Check the cab harness ground stud un-
der the dash, the engine to chassis ground, and the neg-
ative (-) battery cable and ground stud cable near the
hydraulic reservoir fill cap under the engine cover.
The cab must be partially removed to access the fuel
tank. Refer to Section 3.2.3, b. Cab Removal in this man-
ual for cab and fuel tank removal instructions.
Electrical System
10.169