See Figure 1
All 1989-96 diesel engines employ a fuel/water separator, a filter which protects the injection pump by removing water and contaminants from the fuel. The separator filter construction allows fuel to pass through it, but traps water. The water collects at the bottom of the separator filter, so it must be drained periodically. The factory doesn't specify any maintenance interval, but it is advisable to drain the separator filter at least twice a year.
There is a drain at the bottom of the separator filter assembly. Place a drain pan under the drain tube. With the engine turned OFF , push up on the drain to remove the water. Hold the drain open until all the water and contaminants have been removed and clean fuel appears. Dispose of the mixture in the drain pan properly.
- Unplug the electrical connector from the Water In Fuel (WIF) sensor at the bottom of the fuel separator.
- Remove the fuel/water separator filter housing by unscrewing it from the bottom of the fuel heater, much like you'd remove an oil filter.
- Remove the square-cut O-ring from the filter connector at the bottom of the fuel heater.
- Drain the fuel/water separator filter. Remove the WIF sensor, O-ring and fuel/water drain valve assembly from the separator filter.
- Install a new O-ring on the WIF sensor.
- Install the WIF sensor into the new separator filter.
- Fill the unit with clean diesel fuel. If the separator filter is not filled with fuel before being installed, manual air bleeding of the system will be required.
- Apply a light film of clean engine oil to the separator filter seal.
- Install a new square-cut O-ring to the filter connector on the bottom of the fuel heater.
- Install the separator filter. Tighten the assembly 1 / 2 turn after it makes contact, then plug in the electrical connector to the WIF sensor.