Water In Fuel Indicator: Testing and Inspection

Fig. 4 Water in fuel indicator & tank purge procedure. 1982---84 GM with diesel engine:

1982---84
If warning indicator fails to light during bulb check, disconnect wiring harness connector at fuel gauge sending unit, containing a yellow/black stripe wire. With ignition switch in RUN position, connect yellow/black stripe wire to ground, using a suitable jumper wire. If lamp lights, problem is in water detector. If lamp fails to light, check for open circuit between sender and warning lamp, a burned out bulb, or a blown fuse.
If warning lamp remains on at all times, disconnect wiring harness connector at fuel tank sending unit with ignition switch in RUN position. If warning lamp remains on, check for short circuit to ground between sender and warning lamp. If warning lamp goes out when harness is disconnected, first purge water in fuel tank, Fig. 4, then recheck circuit. If lamp remains on with harness connected to sending unit, water detector is defective.