When a problem is indicated by the โWATER IN FUELโ signal light, first follow the diagnostic procedure outlined in the vehicle sen/ice manual. If this procedure fails to locate the problem and the light continues to stay on, the fault may be in the fuel filter/water separator assembly electrical sensors.
To determine which sensor may be at fault, first disconnect the vacuum sensor. To distinguish the electrical leads,
refer to Figure 4-27. The vacuum sensor has two wire leads with a black connector.
If the indicator light goes off, then the vacuum sensor is probably defective and should be replaced according to
the following instructions.
1) Prior to removal of the defective vacuum sensor, obtain a new vacuum sensor and connect to the wire leads in the vehicle. The light should remain off. This is to ensure the new sensor has not been damaged during shipment.
2) Drain the fuel filter/water separator assembly into a container according to the instructions in the vehicle service manual, then disconnect and remove the entire assembly from the vehicle.
3) Remove the filter/separator element from the base assembly.
4) Using a small screwdriver, pry the vacuum sensor retaining clip from the base (Reference Figure 4-27). Take care to prevent damage to the bore. It is suggested that initially prying the clip upwards at the wire lead protective tab will cause the least amount of scoring to the base bore.
5) Remove the vacuum sensor by pulling up on the sensor wire leads and by simultaneously prying under the sensor opposite the leads using a small screwdriver.
6) After the sensor is removed, check the bore by running your finger around the inside of the bore and visually inspect for sharp edges or raised metal burrs caused by removal of the retaining clip.
7) If burrs are present, use a fine (300) grit paper or round stone to remove any sharp metal burrs or scratches in the bore. This is to prevent harm to the sensor โ0โ ring seal during installation. Take care to prevent debris from entering the hole at the bottom of the bore when performing this service.
8) Using a lint-free cloth and solvent, wipe off any debris from the bore area that may have been generated during the deburring process, then blow off the area with compressed air.
9) Remove the sensor retaining clip from the new sensor using a knife blade or screwdriver to pry the clip upward at the wire lead area.
10) Apply a liberal amount of vaseline, grease or STP to the sensor โ0โ ring seal. Also apply a small amount of lubricant to the base sensor bore.
11) See Figure 4-28 for proper vacuum sensor installation. To prevent cutting of the โ0โ ring seal, insert the sensor into the bore at an angle with wire lead portion inserted first. Insert the new sensor (less the retaining clip) into the base, using finger pressure until it is seated or nearly seated at the bottom of the bore.
12) Assure the cellular air filter is in place atop the sensor, then place the sensor retaining clip in position with the protective tab over the wire lead. Holding the retaining clip in position with one finger placed at the center of the clip, work the retainer into place by forcing each tab downward uniformly and in small increments using a screwdriver. The retainer will be in proper position when no further downward movement is felt and the top of the retainer is approximately flush with the lip of the bore.
13) Install filter/separator element to the base assembly.
14) Reinstall fuel filter/water separator assembly to the vehicle. Connect all electrical leads and the fuel inlet line.
Leave the fuel outlet line (smaller) disconnected.
15) Follow the engine startup procedure outlined in the vehicle service manual under โ Fuel Filter โ Replacement (Diesel Engine)โ . When clear fuel is observed coming from the outlet fitting, connect the outlet fuel line and complete the engine startup procedure.