The 1982-83 units used a tank unit mounted water in fuel (W.I.F.) warning-system. It will detect the presence of water when it reaches the 1-2 gallon level. The water is detected by a capacitive probe. An electronic module provides a ground through a wire to a light in the instrument cluster that reads “water in fuel” . The W.I.F. also contains a bulb check. When the ignition is turned on, the bulb will glow from two to five seconds and then fade away.
Owners with water in fuel lights have been instructed to drain the water from the tank if the light comes on immediately after filling. There could be enough water in the system to get into the fuel system and shut the engine down after driving for a short distance. If however it comes on during a cornering or braking maneuver, there is less than a gallon and a shut down will not occur, however, the water should be removed within one or two days. This system will not detect bacteria contained in the water. Figure 4-5 contains diagnostic information on the tank sending unit mounted W.I.F.
A check valve is provided at the upper end of the return pipe to allow fuel to return in the event that frozen water plugs the end of the pipe.
All vehicles using diesel engines have a sock with a bypass valve in the top end. This bypass valve is designed to open up in the event that high cloud point fuels are used in cold weather and the sock gets plugged with wax crystals. The fuel level should be kept at a 1/4 tank, to make sure you do not run out of fuel.
The W.I.F. detector can be serviced separately from the tank unit assembly when it requires replacement. It can be bench checked by using the test setup shown in Figure 4-6.
The module in the detector probe must remain submerged in water for approximately a 15 to 20 second delay period. The indicator lamp will then come on and stay on until the 12V signal is removed. This feature will accommodate large amounts of water.
In 1983, the water in fuel sensitivity was increased to trigger at 1 to 3 liters (.26 to .80 gals.). The time delay was changed from 15-20 seconds to 3-6 seconds.
