The 6.2L uses a water in fuel warning system, which allows the user to guard against water in the fuel.
The water is detected by a capacitive probe located in the filter base. Electronics within the probe will connect a ground (circuit 150) to the ground side of the water in fuel lamp (circuit 508). This lamp is in the center of the instrument panel next to the glow plug lamp. In 1984 (4 wire water sensor module) a bulb check was made any time the ignition switch was in the start position. A B + signal on the purple wire at the โAโ test switch (Figure 4-21) causes pin โ Dโ to pull low, grounding the โwater-in-fuelโ bulb. In 19841/2 and 1985 (3 wire water sensor module) when the ignition is turned on, the lamp will glow from 2 to 5 seconds, and fade away. This is done as a bulb check.
The probe material is iron ferrite, which is not subject to electrolysis. The sensor will turn on at a 50cc level.
