Fuel Sending Unit
IN VEHICLE TEST1. Visually inspect fuel tank for damage.
NOTE: A fuel tank that is collapsed or distorted from its normal shape will seriously affect the fuel indicating system operation. Service or replacement is recommended before further testing. If fuel sender is removed from the fuel tank, refer to bench test procedure.
2. Connect one lead of an ohmmeter to the ground terminal of the fuel sender connector, the other lead to the variable resistor terminal. The ohmmeter should read between 13-17 ohms at EMPTY stop, and 154-166 ohms at FULL stop. If the FULL fuel sender resistance reading is below 154 ohms or above 166 ohms,
3. Using the Rotunda gasoline tanker 34-0002 or equivalent, drain all the fuel from the fuel tank. Observe the ohmmeter reading while the fuel tank is being drained. The resistance should decrease smoothly without jumping or hesitating. If the resistance reading jumps or hesitates,
4. When the fuel tank is empty, the ohmmeter reading should be between 13 and 17 ohms resistance. If the EMPTY fuel tank fuel sender resistance reading is below 13 ohms or above 17 ohms,
5. If the results of the previous steps are OK and an erroneous fuel indication still exists, it is necessary to service the wiring or fuel gauge.
BENCH TEST (sender removed from fuel tank)
NOTE: Check the float assembly. Be sure the float rod is not bent and that the float is not filled with fuel, badly distorted, or loose on float rod.
1. Connect one lead of an ohmmeter to the ground terminal of the fuel sender connector, and the other lead to the variable resistor terminal. The ohmmeter reading should be between 13 and 17 ohms resistance when the float rod is against the EMPTY stop (closest to the fuel filter). If the EMPTY fuel tank fuel sender resistance reading is below 13 ohms or above 17 ohms,
2. Observe the ohmmeter reading while slowly moving the float between the EMPTY and FULL float rod stops. The resistance increase or decrease should be smooth without jumping or hesitation. If the resistance reading jumps or hesitates while slowly moving the float rod,
3. Move the float rod to the FULL stop position (furthest away from the fuel filter). The ohmmeter should read between 154 ohms and 166 ohms resistance. If the ohmmeter resistance reading is below 13 ohms or above 17 ohms,
4. Before installing a fuel sender unit, the wire harness connector should be connected to the fuel sender unit and the float rod moved from the EMPTY to FULL stops to check fuel gauge readings.
NOTE: After moving the float rod from EMPTY to FULL stop position or from FULL stop to EMPTY position, turn ignition key from OFF to RUN or ACC position for fuel gauge indication reading as described in the diagnosis procedures. If steps 1, 2, and 3 of this procedure are OK and the fuel gauge does not indicate properly, perform the fuel gauge system tests, Fuel Gauge System