ISSUE Some 2004-2008 F-Super Duty 650-750 vehicles equipped with dual
fuel tanks, may exhibit one tank emptying and the other tank remaining
full. ACTION Follow the Service Procedure steps to correct the
condition. SERVICE PROCEDURE On 2004-2007 F-Super Duty 650-750
vehicles the right fuel tank will be empty and fuel does not transfer
from the left tank. On 2008 F-Super Duty 650-750 vehicles the left fuel
tank will be empty and fuel does not transfer from the right tank.
Transfer pump diagnostics note both sending units provide input to the
fuel transfer pump (module). Only one sender is also wired to the
instrument cluster. The integral module in the transfer pump controls
the transfer pump operation. Note on 2004-2007 model year vehicles only
the right sender provides fuel level information to the cluster/gauge
and the fuel transfer pump (module). The right tank feeds the engine
fuel system while the left tank feeds only the right tank to maintain
equal fuel levels. Note on 2008 model year vehicles the left sender
provides fuel level information to the cluster/gauge and fuel transfer
pump (module). The left tank feeds the engine fuel system while the
right tank feeds only the left tank to maintain equal fuel levels.
Refer to Wiring Diagram Section 49 for the following diagnostics. At
Connector C3264 (2005-2008), C9102a (2004), located at the fuel transfer
pump, perform the following: 1. Verify the voltage on pin-E (pk/bk
wire) is battery voltage. If concern is found, repair as necessary and
reevaluate transfer pump operation. 2. Verify pin-D (bk/og wire) has a
good ground. If concern is found, repair as necessary and reevaluate
transfer pump operation. 3. Verify the resistance on both sending
units pin-A and pin-B are within the range of 15 Ohms empty to 160 Ohms
full. If concern is found, repair as necessary and reevaluate transfer
pump operation. 4. With all the connectors connected and the key on
engine running (KOER), verify the voltage at alternator (circuit 1818)
is 7-7.5 volts. If voltage is outside this range, load test circuit 1818
(wh/bk wire) to ensure wire integrity. If circuit 1818 integrity is
verified, and voltage is below the specified range, replace alternator.
Refer to Workshop Manual (WSM), Section 414-02. 5. If no concerns are
found with voltage/resistance in steps 1-4, replace the fuel transfer
pump. Refer to WSM, Section 310-01. 6. Verify transfer pump operation
by creating a 10 gallon fuel difference, with the right side tank level
on 2004-2007 model year and left side tank on 2008 model year being
lower. Start the engine and observe fuel transfer pump operation.
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